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Performance Area => Peer Reviewed Studies Discussion => Topic started by: adarqui on June 04, 2009, 08:17:41 pm
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All conclusions of studies will be listed in this original post (TABLE OF SUMMARIES) for quick reference.
This thread goes out to our dear friend CoolColJ:
Post anything related to Sleep, Biological Rhythms, or Stress and its effect on performance.
1A. Elevations in core and muscle temperature impairs repeated sprint performance
Conclusion: Although an elevated muscle temperature is expected to promote sprint performance, power output during the repeated sprints was reduced by hyperthermia. The impaired performance does not seem to relate to the accumulation of recognized metabolic fatigue agents and we, therefore, suggest that it may relate to the influence of high core temperature on the function of the central nervous system.
1. Electro-mechanical response times and muscle strength after sleep deprivation.
The results suggest that subjects who have undergone 60 h of SD can react as fast, and with as much force, as those who have had 7 h of sleep per night.
2. Physical performance and physiological responses following 60 hours of sleep deprivation.
These results suggest that sleep loss of up to 60 h will not impair the capability for physical work, a finding of considerable importance in sustained military operations which frequently involve the combination of both physical and mental tasks.
3. The effect of partial sleep deprivation on weight-lifting performance
Results indicate that submaximal lifting tasks are more affected by sleep loss than are maximal efforts, particularly for the first two nights of successive sleep restriction.
4. Effects of caffeine, sleep loss, and stress on cognitive performance and mood during U.S. Navy SEAL training
Sleep deprivation and environmental stress adversely affected performance and mood. Caffeine, in a dose-dependent manner, mitigated many adverse effects of exposure to multiple stressors. Caffeine (200 and 300 mg) significantly improved visual vigilance, choice reaction time, repeated acquisition, self-reported fatigue and sleepiness with the greatest effects on tests of vigilance, reaction time, and alertness. Marksmanship, a task that requires fine motor coordination and steadiness, was not affected by caffeine. The greatest effects of caffeine were present 1 h post-administration, but significant effects persisted for 8 h.
5. Caffeine effects on marksmanship during high-stress military training with 72 hour sleep deprivation.
Sighting time was significantly faster in sleep deprived individuals after taking 200 or 300 mg of caffeine compared with placebo or 100 mg of caffeine. No differences in accuracy measures between caffeine treatment groups were evident at any test period. CONCLUSION: During periods of sleep deprivation combined with other stressors, the use of 200 or 300 mg of caffeine enabled SEAL trainees to sight the target and pull the trigger faster without compromising shooting accuracy.
6. Sleep-dependent learning: a nap is as good as a night
Thus, from the perspective of behavioral improvement, a nap is as good as a night of sleep for learning on this perceptual task.
7. The effects of two alternative timings of a one-hour nap on early morning performance.
It was concluded that a one-hour nap could counteract the late night performance decrement.
8. Effects of Exercise, Bedrest and Napping on Performance Decrement During 40 Hours
... and naps reduce or remove this impairment. Bedrest is not a substitute for sleep.
9. Impact of Ramadan on physical performance in professional soccer players
Performance declined significantly (p<0.05) for speed, agility, dribbling speed and endurance, and most stayed low after the conclusion of Ramadan. Nearly 70% of the players thought that their training and performance were adversely affected during the fast.
10. Physical performance responses during 72 h of military operational stress.
Results: Fat-free mass (-2.3%) and fat mass (-7.3%) declined (P <= 0.05) during SUSOPS. Squat-jump mean power (-9%) and total work (-15%) declined (P <= 0.05) during SUSOPS. Bench-press power output, grenade throw, and marksmanship for pop-up targets were not affected. Obstacle course and box-lift performances were lower (P <= 0.05) on D3 but showed some recovery on D4. Wall building was ~25% lower (P <= 0.05) during SUSOPS.
11. Circadian variation in sports performance.
Atkinson G, Reilly T.
Centre for Sport and Exercise Sciences, School of Human Sciences, Liverpool John Moores University, England.
Chronobiology is the science concerned with investigations of time-dependent changes in physiological variables. Circadian rhythms refer to variations that recur every 24 hours. Many physiological circadian rhythms at rest are endogenously controlled, and persist when an individual is isolated from environmental fluctuations. Unlike physiological variables, human performance cannot be monitored continuously in order to describe circadian rhythmicity. Experimental studies of the effect of circadian rhythms on performance need to be carefully designed in order to control for serial fatigue effects and to minimise disturbances in sleep. The detection of rhythmicity in performance variables is also highly influenced by the degree of test-retest repeatability of the measuring equipment. The majority of components of sports performance, e.g. flexibility, muscle strength, short term high power output, vary with time of day in a sinusoidal manner and peak in the early evening close to the daily maximum in body temperature. Psychological tests of short term memory, heart rate-based tests of physical fitness, and prolonged submaximal exercise performance carried out in hot conditions show peak times in the morning. Heart rate-based tests of work capacity appear to peak in the morning because the heart rate responses to exercise are minimal at this time of day. Post-lunch declines are evident with performance variables such as muscle strength, especially if measured frequently enough and sequentially within a 24-hour period to cause fatigue in individuals. More research work is needed to ascertain whether performance in tasks demanding fine motor control varies with time of day. Metabolic and respiratory rhythms are flattened when exercise becomes strenuous whilst the body temperature rhythm persists during maximal exercise. Higher work-rates are selected spontaneously in the early evening. At present, it is not known whether time of day influences the responses of a set training regimen (one in which the training stimulus does not vary with time of day) for endurance, strength, or the learning of motor skills. The normal circadian rhythms can be desynchronised following a flight across several time zones or a transfer to nocturnal work shifts. Although athletes show all the symptoms of 'jet lag' (increased fatigue, disturbed sleep and circadian rhythms), more research work is needed to identify the effects of transmeridian travel on the actual performances of elite sports competitors. Such investigations would need to be chronobiological, i.e. monitor performance at several times on several post-flight days, and take into account direction of travel, time of day of competition and the various performance components involved in a particular sport. Shiftwork interferes with participation in competitive sport, although there may be greater opportunities for shiftworkers to train in the hours of daylight for individual sports such as cycling and swimming. Studies should be conducted to ascertain whether shiftwork-mediated rhythm disturbances affect sports performance. Individual differences in performance rhythms are small but significant. Circadian rhythms are larger in amplitude in physically fit individuals than sedentary individuals. Athletes over 50 years of age tend to be higher in 'morningness', habitually scheduling relatively more training in the morning and selecting relatively higher work-rates during exercise compared with young athletes. These differences should be recognised by practitioners concerned with organising the habitual regimens of athletes.
12. Circadian rhythms in two types of anaerobic cycle leg exercise: force-velocity and 30-s Wingate tests.
Souissi N, Gauthier A, Sesboüé B, Larue J, Davenne D.
The results indicated that oral temperature, P (peak), P (mean) and P (max) varied concomitantly during the day. These results suggest that there was a circadian rhythm in anaerobic performance during cycle tests. The recording of oral temperature allows one to estimate the time of occurrence of maximal and minimal values in the circadian rhythm of anaerobic performance.
13. Sports, Sleep, and Circadian Rhythms : Circadian Rhythms and Enhanced Athletic Performance in the National Football League
Circadian rhythms produce daily changes in critical elements of athletic performance. We explored the significance of performing at different circadian times in the national football league (NFL) over the last 25 seasons. West coast (WC) nfl teams should have a circadian advantage over east coast (EC) teams during monday night football (MNF) games because WC teams are essentially playing closer to the proposed peak athletic performance time of day. Retrospectice data analysis was applied to all games involving WC versus EC teams playing on MNF with start times of 9:00 pm Eastern Standard Time (EST) from 1970-1994 seasons. Logistic regression analysis of win-loss records relative to point spreads and home-field advantage were examined. West Coast Teams win more often (p < 0.01) and by more points per game than EC teams. West Coast teams are performing significantly (p < 0.01) better than is predicted by the Las Vegas odds (the point spread). This apparent advantage enhances home-field advantage for WC teams and essentially eliminates the beneficial effects of home-field advantage for EC teams during MNF games. These results support the presence of an enhancement of athletic performance at certain circadian times of the day.
14. Diurnal Rhythm of the Muscular Performance of Elbow Flexors During Isometric Contractions
We also assessed variations in the level of maximal activity of the muscle under maximal voluntary contraction. Neuromuscular efficiency fluctuated during the day, with maximal and minimal efficiency at 18:00 h and 9:00 h, respectively, whereas activation level was maximal at 18:00 h and minimal at 9:00 h. The diurnal rhythm of torque was accounted for by variations in both central nervous system command and the contractile state of the muscle.
15. Circadian performance differences between morning and evening 'types'
significant differences were apparent with the number of items correctly rejected. M (MORNING) types' correct rejection levels were significantly better than E (EVENING) types' in the morning, whereas they were worse during the evening. Whilst E types showed a steady improvement throughout the day, M types showed a general decline. A post-lunch dip in performance was quite evident for M types, but not for E types. In addition, the circadian trends in correct rejection levels and body temperature were highly positively correlated for E types, but a significant negative relationship between these parameters was found for M types. These findings are discussed.
16. CIRCADIAN RHYTHMS IN HUMAN MUSCULAR EFFICIENCY: CONTINUOUS PHYSICAL EXERCISE VERSUS CONTINUOUS REST. A CROSSOVER STUDY
Despite the standardized conditions, the results showed that isometric maximal strength varied with time of day during both a submaximal exercise and at rest without prior exercise. The sine waves representing these two rhythms were correlated significantly. Although at rest the diurnal rhythm followed muscular activity (i.e., neurophysiological factors), during exercise, this rhythm was thought to stem more from fluctuations in the contractile state of muscle. (Chronobiology International, 17(5), 693-704, 2000)
17. Circadian rhythms have no effect on cycling performance
Resting oral temperature was the only variable to show a significant time of day effect (p<0.05). Oral temperature during the afternoon was higher than both morning and evening results by 0.76°C and 0.09°C respectively. Although athletic performance may be enhanced by training programs that are compatible with an individuals body clock, the ability to perform and train at various times has an adaptive response which appears to over-ride these naturally inherent rhythms.
18. Time-of-day dependence of isokinetic leg strength and associated interday variability.
This finding appears to be consistent with current knowledge about time-of-day effects on the assessment of muscular strength. Thus for stable and maximal values to be obtained during isokinetic leg testing, the use of multiple-trial protocols is recommended, with testing occurring as close to 18.00-19.30 hours as possible. In addition, the observed significant time-of-day effect suggests that appropriate comparison of maximal isokinetic leg strength can only be achieved based on data obtained within 30 min of the same time of day.
19. Effects of dehydration on isometric muscular strength and endurance.
These results provide evidence that isometric strength and endurance are unaffected 3.5 h after dehydration of approximately 4% body mass.
20. Sleep deprivation induced anxiety and anaerobic performance
Neither anaerobic pa-
rameters nor state anxiety levels were affected by one night
partial sleep deprivation. Our results suggest that 30 hours con-
tinuous wakefulness may increase anxiety level without impair-
ing anaerobic performance, whereas one night of partial sleep
deprivation was ineffective on both state anxiety and anaerobic
performance.
21. The role of a short post-lunch nap in improving cognitive, motor, and sprint performance in participants with partial sleep deprivation
These results indicate that a post-lunch nap improves alertness and aspects of mental and physical performance following partial sleep loss, and have implications for athletes with restricted sleep during training or before competition.
22. Effects of One Night of Partial Sleep Deprivation upon Diurnal Rhythms of Accuracy and Consistency in Throwing Darts
Increasing time awake was associated with decreased alertness and increased fatigue, as well as slight negative effects upon performance. We conclude that the simple task of throwing darts at a target provides information about chronobiological changes in circumstances where time awake and sleep loss might affect psychomotor performance.
23. Effects of a selective sleep deprivation on subsequent anaerobic performance
The peak power, the mean power output and the peak velocity recorded after partial sleep deprivation were not modified in comparison with the values obtained after the reference night. These findings suggest that acute sleep loss did not contribute to alterations in supramaximal exercise.
24. Effects of one night's sleep deprivation on anaerobic performance the following day
Up to 24 h of waking, anaerobic power variables were not affected; however, they were impaired after 36 h without sleep. Analysis of variance revealed that blood lactate concentrations were unaffected by sleep loss, by time of day of testing or by the interaction of the two. In conclusion, sleep deprivation reduced the difference between morning and afternoon in anaerobic power variables. Anaerobic performances were unaffected after 24 h of wakefulness but were impaired after 36 h without sleep.
25. Sleep deprivation and exercise
Concerning anaerobic power and strength, significant alterations have not been found; however, for prolonged events there may be an interaction between these two factors, which suggests a protection mechanism. Nevertheless, it is important to consider that one of the main alterations caused by sleep deprivation the increase of the subjective perception, which presents a factor to decrease and compromise the physical performance per se, and may represent a masking element of the deleterious effects of sleep deprivation. Thus, the aim of present review is to discuss the different aspects of relationship between physical exercise and sleep deprivation, showing their effects and consequences in physical performance.
26. The Impact of Sleep Deprivation on Decision Making: A Review
Few sleep deprivation (SD) studies involve realism or high-level decision making, factors relevant to managers, military commanders, and so forth, who are undergoing prolonged work during crises. Instead, research has favored simple tasks sensitive to SD mostly because of their dull monotony. In contrast, complex -based, convergent, and logical tasks are unaffected by short-term SD, seemingly because of heightened participant interest and compensatory effort. However, recent findings show that despite this effort, SD still impairs decision making involving the unexpected, innovation, revising plans, competing distraction, and effective communication. Decision-making models developed outside SD provide useful perspectives on these latter effects, as does a neuropsychological explanation of sleep function. SD presents particular difficulties for sleep-deprived decision makers who require these latter skills during emergency situations.
27. The Acute Effects of Twenty-Four Hours of Sleep Loss on the Performance of National-Caliber Male Collegiate Weightlifters
Currently, the degree to which sleep loss influences weightlifting performance is unknown. This study compared the effects of 24 hours of sleep loss on weightlifting performance and subjective ratings of psychological states pre-exercise and postexercise in national-caliber male collegiate weightlifters. Nine males performed a maximal weightlifting protocol following 24 hours of sleep loss and a night of normal sleep. The subjects participated in a randomized, counterbalanced design with each sleep condition separated by 7 days. Testosterone and cortisol levels were quantified prior to, immediately after, and 1 hour after the resistance training session. Additionally, profile of mood states and subjective sleepiness were evaluated at the same time points. The resistance training protocol consisted of several sets of snatches, clean and jerks, and front squats. Performance was evaluated as individual exercise volume load, training intensity and overall workout volume load, and training intensity. During each training session the maximum weight lifted for the snatch, clean and jerk, and front squat were noted. No significant differences were found for any of the performance variables. A significant decrease following the sleep condition was noted for cortisol concentration immediately after and 1 hour postexercise. Vigor, fatigue, confusion, total mood disturbance, and sleepiness were all significantly altered by sleep loss. These data suggest that 24 hours of sleep loss has no adverse effects on weightlifting performance. If an athlete is in an acute period of sleep loss, as noticed by negative mood disturbances, it may be more beneficial to focus on the psychological (motivation) rather than the physiological aspect of the sport.
28. Effect of sleep deprivation on tolerance of prolonged exercise
These findings suggest that the psychological effects of acute sleep loss may contribute to decreased tolerance of prolonged heavy exercise.
29. Sleep deprivation and cardiorespiratory function
Physiological responses to sub-maximal exercise showed persistence of the normal diurnal rhythm in heart rate and oxygen consumption, with no added effects due to sleep deprivation. However, ratings of perceived exertion (Borg scale) increased significantly throughout sleep deprivation. The findings are consistent with a mild respiratory acidosis, secondary to reduced cortical arousal and/or a progressive depletion of tissue glycogen stores which are not altered appreciably by moderate physical activity.
30. Caffeine Use in Sports: Considerations for the Athlete.
caffeine can be taken gradually at low doses to avoid tolerance during the course of 3 or 4 days, just before intense training to sustain exercise intensity; and caffeine can improve cognitive aspects of performance, such as concentration, when an athlete has not slept well. Athletes and coaches also must consider how a person's body size, age, gender, previous use, level of tolerance, and the dose itself all influence the ergogenic effects of caffeine on sports performance.
31. Effects of Caffeine on Prolonged Intermittent-Sprint Ability in Team-Sport Athletes.
Conclusion: This study revealed that acute caffeine ingestion can significantly enhance performance of prolonged, intermittent-sprint ability in competitive, male, team-sport athletes.
32. Maximal aerobic exercise following prolonged sleep deprivation.
The effect of 60 h without sleep upon maximal oxygen intake was examined in 12 young women, using a cycle ergometer protocol. The arousal of the subjects was maintained by requiring the performance of a sequence of cognitive tasks throughout the experimental period. Well-defined oxygen intake plateaus were obtained both before and after sleep deprivation, and no change of maximal oxygen intake was observed immediately following sleep deprivation. The endurance time for exhausting exercise also remained unchanged, as did such markers of aerobic performance as peak exercise ventilation, peak heart rate, peak respiratory gas exchange ratio, and peak blood lactate.
33. Multiple Effects of Caffeine on Simulated High-Intensity Team-Sport Performance.
The effects of caffeine on mean performance (+/-90% confidence limits) over all 14 circuits were: sprint speeds, 0.5% (+/-1.7%) through 2.9% (+/-1.3%); first-drive power, 5.0% (+/-2.5%); second-drive power, -1.2% (+/-6.8%); and passing accuracy, 9.6% (+/-6.1%). The enhancements were mediated partly through a reduction of fatigue that developed throughout the test and partly by enhanced performance for some measures from the first circuit. Caffeine produced a 51% (+/-11%) increase in mean epinephrine concentration; correlations between individual changes in epinephrine concentration and changes in performance were mostly unclear, but there were some strong positive correlations with sprint speeds and a strong negative correlation with passing accuracy. Conclusion: Caffeine is likely to produce substantial enhancement of several aspects of high-intensity team-sport performance.
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Time-course of Changes in Inflammatory and Performance Responses Following a Soccer Game: 2328: Board #108 May 30 3:30 PM - 5:00 PM
[F-23 Free Communication/Poster - Exercise Immunology: MAY 30, 2008 1:00 PM - 6:00 PM: ROOM: Hall B]
Fatouros, Ioannis G.1; Chatzinikolaou, Athanasios1; Ispirlidis, Ioannis1; Jamurtas, Athanasios Z.2; Nikolaidis, Michalis G.3; Michailidis, Ioannis4; Douroudos, Ioannis1; Margonis, Konstantinos1; Taxildaris, Kiriakos1
1Democritus University of Thrace, Department of Physical Education & Sport Science, Komotini, Greece. 2University Of Thessaly, Department Of Physical Education & Sports Sciences, Trikala, Greece. 3Institute of Human Performance and Rehabilitation, Centre for Research and Technology, TRIKALA, Greece. 4Democritus University Of Thrace, Komotini, Greece.
Email: fatouros@otenet.gr
(No relationships reported)
A competitive soccer season includes weekly micro-cycles consisting of training, taper, competition, and recovery. The ability of soccer players to fully recover prior to their next major competition is crucial not only for their performance but for injury prevention as well. Information on the time-course of changes in the acute phase inflammatory response, soreness, pain, and performance after a single soccer game is scarce.
PURPOSE: to study the effects of a single soccer game on indices of performance, muscle damage and inflammation during a 6-day recovery period.
METHODS: Twenty-four elite male soccer players (20.1 ± 0.8 yrs, 1.78 ± 0.08 m, 75.2 ± 6.8 kg) were assigned to either an experimental group (E, n=14, played in a game) or a control group (C, n=10, did not participate in the game). Muscle strength, vertical jumping, speed, DOMS, muscle swelling, leukocyte count, creatine kinase (CK), lactate dehydrogenase (LDH), C-reactive protein (CRP), cortisol, testosterone, cytokines IL-6 and IL-1?, TBARS, protein carbnyls (PC) and uric acid were measured prior to the game and immediately post-game as well as 24, 48, 72, 96, 120, and 144 hours following the game.
RESULTS: VJ decreased (P<0.05) 24-h after the game and returned to pre-game values 72-h following the game. 1RM decreased (P<0.05) after the game, reached its lowest value at 48-h post-game, and returned to pre-game levels 96-h after the game. Sprinting ability declined (P<0.05) post-game, reached its lowest value 48-h post-game, and returned to pregame levels after 120-h. An acute phase inflammatory response consisted of a post-game peak of leukocyte count, cytokines and cortisol, a 24 h peak of CRP, TBARS, and DOMS, a 48 h peak of CK, LDH, and PC, and a 72 h peak of uric acid.
CONCLUSIONS: a single soccer game induces short-term muscle damage and marked but transient inflammatory responses. Anaerobic performance seems to deteriorate for as long as 72 h post-game. The acute phase inflammatory response in soccer appears to follow the same pattern as in other forms of exercise. These results clearly indicate the need of sufficient recovery for elite soccer players following a game.
Maximal aerobic exercise following prolonged sleep deprivation.
The effect of 60 h without sleep upon maximal oxygen intake was examined in 12 young women, using a cycle ergometer protocol. The arousal of the subjects was maintained by requiring the performance of a sequence of cognitive tasks throughout the experimental period. Well-defined oxygen intake plateaus were obtained both before and after sleep deprivation, and no change of maximal oxygen intake was observed immediately following sleep deprivation. The endurance time for exhausting exercise also remained unchanged, as did such markers of aerobic performance as peak exercise ventilation, peak heart rate, peak respiratory gas exchange ratio, and peak blood lactate. However, as in an earlier study of sleep deprivation with male subjects (in which a decrease of treadmill maximal oxygen intake was observed), the formula of Dill and Costill (4) indicated the development of a substantial (11.6%) increase of estimated plasma volume percentage with corresponding decreases in hematocrit and red cell count. Possible factors sustaining maximal oxygen intake under the conditions of the present experiment include (1) maintained arousal of the subjects with no decrease in peak exercise ventilation or the related respiratory work and (2) use of a cycle ergometer rather than a treadmill test with possible concurrent differences in the impact of hematocrit levels and plasma volume expansion upon peak cardiac output and thus oxygen delivery to the working muscles.
Effects of Caffeine on Prolonged Intermittent-Sprint Ability in Team-Sport Athletes.
APPLIED SCIENCES
Medicine & Science in Sports & Exercise. 38(3):578-585, March 2006.
SCHNEIKER, KNUT THOMAS 1; BISHOP, DAVID 1; DAWSON, BRIAN 1; HACKETT, LAURENCE PETER 2
Abstract:
Purpose: Caffeine can be a powerful ergogenic aid for the performance of prolonged, submaximal exercise. Little evidence, however, supports an ergogenic effect of caffeine on intermittent-sprint performance. Hence, this study was conducted to examine the effects of acute caffeine ingestion on prolonged intermittent-sprint performance.
Methods: Using a double-blind, placebo-controlled design, 10 male team-sport athletes (amateur level, [latin capital V with dot above]O2peak 56.5 +/- 8.0 mL[middle dot]kg-1[middle dot]min-1) completed two exercise trials, separated by 7 d, 60 min after ingestion of either 6 mg[middle dot]kg-1 caffeine or placebo. The exercise trial was performed on a front-access cycle ergometer and consisted of 2 x 36-min halves, each composed of 18 x 4-s sprints with 2-min active recovery at 35% [latin capital V with dot above]O2peak between each sprint. Urinary caffeine levels were measured after exercise.
Results: The total amount of sprint work performed during the caffeine trial was 8.5% greater than that performed during the placebo trial in the first half (75,165.4 +/- 3,902.9 vs 69,265.6 +/- 3,719.7 J, P < 0.05), and was 7.6% greater in the second half (73,978.7 +/- 4,092.6 vs 68,783.2 +/- 3,574.4 J, P < 0.05). Similarly, the mean peak power score achieved during sprints in the caffeine trial was 7.0% greater than that achieved during the placebo trial in the first half (1330.9 +/- 68.2 vs 1244.2 +/- 60.7 W, P < 0.05), and was 6.6% greater in the second half (1314.5 +/- 68.4 vs 1233.2 +/- 59.9 W, P < 0.05). Urinary caffeine levels following the caffeine trial ranged from 3.5 to 9.1 [mu]g[middle dot]mL-1 (6.9 +/- 0.6 [mu]g[middle dot]mL-1).
Conclusion: This study revealed that acute caffeine ingestion can significantly enhance performance of prolonged, intermittent-sprint ability in competitive, male, team-sport athletes.
Caffeine Use in Sports: Considerations for the Athlete.
Abstract:
The ergogenic effects of caffeine on athletic performance have been shown in many studies, and its broad range of metabolic, hormonal, and physiologic effects has been recorded, as this review of the literature shows. However, few caffeine studies have been published to include cognitive and physiologic considerations for the athlete. The following practical recommendations consider the global effects of caffeine on the body: Lower doses can be as effective as higher doses during exercise performance without any negative coincidence; after a period of cessation, restarting caffeine intake at a low amount before performance can provide the same ergogenic effects as acute intake; caffeine can be taken gradually at low doses to avoid tolerance during the course of 3 or 4 days, just before intense training to sustain exercise intensity; and caffeine can improve cognitive aspects of performance, such as concentration, when an athlete has not slept well. Athletes and coaches also must consider how a person's body size, age, gender, previous use, level of tolerance, and the dose itself all influence the ergogenic effects of caffeine on sports performance.
Electro-mechanical response times and muscle strength after sleep deprivation.
This study examined the effect of 60 h of sleep deprivation (SD) on electromechanical response times (EMRT), maximal voluntary isometric contraction (MVC), rate of force development (RFD), and times required to reach various percentages of MVC, during a maximal voluntary isometric contraction of both the forearm flexors and leg extensors. Eleven male subjects were either sleep deprived for 60 h (E) or performed similar daily activities and slept 7 h per night (C). Performance variables were evaluated at the same time intervals during both conditions. No significant differences were observed between the E and C conditions for EMRT (pre-motor time, electro-mechanical delay, total reaction time) or muscular performance (MVC, RFD). The results suggest that subjects who have undergone 60 h of SD can react as fast, and with as much force, as those who have had 7 h of sleep per night.
Physical performance and physiological responses following 60 hours of sleep deprivation.
Original Investigations
Medicine & Science in Sports & Exercise. 20(4):374-380, August 1988.
SYMONS, J D; VANHELDER, T; MYLES, W S
Abstract:
SYMONS, J. D., T. VANHELDER, and W. S. MYLES. Physical performance and physiological responses following 60 hours of sleep deprivation. Med. Sci. Sports Exerc, Vol. 20, No. 4, pp. 374-380, 1988. The effect of 60 h of sleep deprivation (SD) upon physical performance and physiological responses to exercise was examined in 11 male subjects. The experiment consisted of two conditions separated by at least 10 d. In the experimental condition (E) subjects remained awake for 60 h and in the control condition (C) the same subjects had 7 h of sleep per night. In both conditions subjects reported to the laboratory on the evening prior to d 1 and slept for 7 h. Physical performance testing was carried out on d 1 and again on d 3 after either two nights of sleep or two nights of SD. Results obtained on d 3 are expressed relative to d 1, the control day. Maximal isometric and isokinetic muscular strength and endurance of selected upper and lower body muscle groups, performance of the Wingate Anaerobic Power Test, simple reaction time, the blood lactate response to cycle exercise at 70% [latin capital V with dot above]O2max, and most of the cardiovascular and respiratory responses to treadmill running at 70% and 80% [latin capital V with dot above]O2max, were not significantly altered as a result of SD. These results suggest that sleep loss of up to 60 h will not impair the capability for physical work, a finding of considerable importance in sustained military operations which frequently involve the combination of both physical and mental tasks.
The effect of partial sleep deprivation on weight-lifting performance
Abstract
This study examined the effects of partial sleep deprivation on submaximal and maximal weight-lifting tasks and on subjective states pre- and post-activity. Eight male subjects (aged 18-24 years) were restricted to a nightly ration of 3 h sleep for 3 successive nights after baseline measures on the first day. A 4 day period where normal sleep was permitted fulfilled a control condition, the normal and sleep-deprived conditions being counterbalanced and separated by 10 days. The weight-lifting tasks consisted of biceps curl, bench press, leg press, and dead lift. For each exercise a submaximal load, corresponding to a fixed value on a category ratio scale of exertion, was determined for 20 repetitions; the maximal lift for that exercise was then obtained. A profile of mood states and subjective sleepiness were determined at each test occasion, tests being conducted in the evening of each day. There was no significant effect of sleep loss on performance of maximal biceps curl (p > 0.05) but a significant effect was noted on maximal bench press, leg press, and dead lift (p < 0.001). Trend analysis indicated decreased performance in submaximal lifts for all the 4 tasks: the deterioration was significant after the second night of sleep loss (p<0.01). Performing the lifts had little influence on sleepiness ratings which increased linearly with successive days of sleep loss. Mood states of confusion, vigour, and fatigue were affected significantly by the sleep deprivation regimen (p < 0.001), but there was no significant effect of sleep loss or anger, tension, and depression (p > 0-05). Results indicate that submaximal lifting tasks are more affected by sleep loss than are maximal efforts, particularly for the first two nights of successive sleep restriction.
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Effects of caffeine, sleep loss, and stress on cognitive performance and mood during U.S. Navy SEAL training
Rationale. When humans are acutely exposed to multiple stressors, cognitive performance is substantially degraded. Few practical strategies are available to sustain performance under such conditions.
Objective. This study examined whether moderate doses of caffeine would reduce adverse effects of sleep deprivation and exposure to severe environmental and operational stress on cognitive performance.
Methods. Volunteers were 68 U.S. Navy Sea-Air-Land (SEAL) trainees, randomly assigned to receive either 100, 200, or 300 mg caffeine or placebo in capsule form after 72 h of sleep deprivation and continuous exposure to other stressors. Cognitive tests administered included scanning visual vigilance, four-choice visual reaction time, a matching-to-sample working memory task and a repeated acquisition test of motor learning and memory. Mood state, marksmanship, and saliva caffeine were also assessed. Testing was conducted 1 and 8 h after treatment.
Results. Sleep deprivation and environmental stress adversely affected performance and mood. Caffeine, in a dose-dependent manner, mitigated many adverse effects of exposure to multiple stressors. Caffeine (200 and 300 mg) significantly improved visual vigilance, choice reaction time, repeated acquisition, self-reported fatigue and sleepiness with the greatest effects on tests of vigilance, reaction time, and alertness. Marksmanship, a task that requires fine motor coordination and steadiness, was not affected by caffeine. The greatest effects of caffeine were present 1 h post-administration, but significant effects persisted for 8 h.
Conclusions. Even in the most adverse circumstances, moderate doses of caffeine can improve cognitive function, including vigilance, learning, memory, and mood state. When cognitive performance is critical and must be maintained during exposure to severe stress, administration of caffeine may provide a significant advantage. A dose of 200 mg appears to be optimal under such conditions.
The effects of two alternative timings of a one-hour nap on early morning performance.
The effect on performance and sleepiness of two alternative timings of a one-hour nap (2100h and 0430h, respectively) were compared with a control condition (no nap). Twelve healthy male subjects divided into three groups participated in a partly balanced repeated measurements design. At all three occasions the subjects slept 4 h during the preceding night, worked during the day and were then kept awake (except for naps) in the laboratory from 1700h to 0800h the following morning. Performance was measured through a 10-min single choice visual reaction time task administered at 1900h and 0700h. Sleepiness was measured through self-ratings and sleep latency tests at 2100h and 0600h. The results showed clear positive effects of naps (especially the 0430h nap) on performance. The sleep latency measurements showed similar, but less clear tendencies, while ratings of sleepiness did not differentiate between conditions. It was concluded that a one-hour nap could counteract the late night performance decrement.
Caffeine effects on marksmanship during high-stress military training with 72 hour sleep deprivation.
PURPOSE: Navy SEALs (sea, air, land) are elite special warfare units that conduct unconventional warfare primarily in marine environments. Marksmanship accuracy and sighting time were quantified with 62 male trainees during Navy SEAL Hell Week, which involves the combined stress of sleep loss, operational combat scenarios, and cold-wet environmental conditions. Caffeine was administered to minimize deficits due to sleep deprivation. METHODS: Volunteers dry-fired a disabled rifle equipped with a laser-based marksmanship simulator system to measure shooting speed and accuracy. The target was a 2.3-cm diameter circle at a distance of 5 m, simulating a 46 cm target at a distance of 50 m. Marksmanship was assessed prior to training, and at 73 and 80 h into Hell Week. Volunteers were randomly assigned to 1 of 4 treatments: 100, 200, or 300 mg of caffeine or a placebo. Dosing occurred 72 h after training commenced. RESULTS: The combined effects of almost 73 h of total sleep deprivation and operational and environmental stress degraded all marksmanship accuracy measures (p < 0.05) as shown by the 37.5% increase in percent of targets missed, 38% increase in distance from center of mass of the target, and the 235% increase in shot group tightness. Sighting time increased by 53% or 3.1 s after 73 h of sleep deprivation (p < 0.05). Sighting time was significantly faster in sleep deprived individuals after taking 200 or 300 mg of caffeine compared with placebo or 100 mg of caffeine. No differences in accuracy measures between caffeine treatment groups were evident at any test period. CONCLUSION: During periods of sleep deprivation combined with other stressors, the use of 200 or 300 mg of caffeine enabled SEAL trainees to sight the target and pull the trigger faster without compromising shooting accuracy.
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Effects of Exercise, Bedrest and Napping on Performance Decrement During 40 Hours
Young male Naval volunteers were denied normal noclurnal sleep and maintained on a 60-min lreatment-160-min testing schedule during 40 consecutive hrs. Ten subjects bicycled, 20 subjects controlled EEG activity during bedrest, and 10 subjects napped. Eight measures of addition, auditory vigilance, mood, and oral temperature were obtained. The Bedrest group showed significant impairment on all eight measures, and thus, gave no support to lite forced-rest theory of sleep function. The Exercise group was worse than the Nap and Bedrest groups for all measures. In spite of fragmented, reduced sleep (about 3.7 hrs per 24 hrs), the Nap group had no impairment on six of the measures. The results suggest that exercise increases the impairment due to sleep loss, and naps reduce or remove this impairment. Bedrest is not a substitute for sleep.
Sleep-dependent learning: a nap is as good as a night
The learning of perceptual skills has been shown in some cases to depend on the plasticity of the visual cortex1 and to require post-training nocturnal sleep2. We now report that sleep-dependent learning of a texture discrimination task can be accomplished in humans by brief (60? 90 min) naps containing both slow-wave sleep (SWS) and rapid eye movement (REM) sleep. This nap-dependent learning closely resembled that previously reported for an 8-h night of sleep in terms of magnitude, sleep-stage dependency and retinotopic specificity, and it was additive to subsequent sleep-dependent improvement, such that performance over 24 h showed as much learning as is normally seen after twice that length of time. Thus, from the perspective of behavioral improvement, a nap is as good as a night of sleep for learning on this perceptual task.
Impact of Ramadan on physical performance in professional soccer players
ABSTRACT
Objective: Ramadan is a period of daylight abstention from liquid or solid nutrients. As sports continue to be scheduled, an understanding of the effects of Ramadan on Muslim athletes is warranted.
Design: Two Algerian professional soccer teams (55 men) were studied. Field tests of physical and soccer performance were collected before, at the end and 2 weeks after Ramadan in 2004. Players were queried on sleeping habits and personal perception of training and match performance.
Setting: Field setting at club training ground.
Main outcome measures: Performance on fitness and skill tests.
Results: Performance declined significantly (p<0.05) for speed, agility, dribbling speed and endurance, and most stayed low after the conclusion of Ramadan. Nearly 70% of the players thought that their training and performance were adversely affected during the fast.
Conclusions: The phase shift of food intake and disruption of sleep patterns affect actual and perceived physical performance. Islamic athletes need to explore strategies that will maximise performance during Ramadan.
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1. Electro-mechanical response times and muscle strength after sleep deprivation.
The results suggest that subjects who have undergone 60 h of SD can react as fast, and with as much force, as those who have had 7 h of sleep per night.
2. Physical performance and physiological responses following 60 hours of sleep deprivation.
These results suggest that sleep loss of up to 60 h will not impair the capability for physical work, a finding of considerable importance in sustained military operations which frequently involve the combination of both physical and mental tasks.
3. The effect of partial sleep deprivation on weight-lifting performance
Results indicate that submaximal lifting tasks are more affected by sleep loss than are maximal efforts, particularly for the first two nights of successive sleep restriction.
7. The effects of two alternative timings of a one-hour nap on early morning performance.
It was concluded that a one-hour nap could counteract the late night performance decrement.
1,2, and 3 make it seem like it would be better to skip sleep altogether than to sleep for a short time the night before some type of athletic event. However, 7 looks like it says the opposite.
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nah, those studies are just showing you that reaction time/performance etc is not as effected by sleep deprivation as we might think.. and when you factor caffiene into the equation, performance level can be near optimal.
as for #7, it's saying that taking a nap could decrease the effect of only having 4 hours sleep.
it's never good to not sleep at all when you have a performance test/event the day after... but, if you are somehow unable to sleep, just have the confidence that a shitload of caffeine will help you perform at near optimal levels ;)
edit: i mean how many times have you been so excited about the next day, that your sleep suffers? it's great to know that you can still perform... it happens to me every time I have something big planned the next day, like trying to for some PR dunks.. once I started telling myself "it doesn't matter if i sleep or not, i'll still jump good", it got out of my head... and studies like this have only help me sleep better because I stop worrying about it ;) alot of these studies are from my huge notes file hehe..
peace
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Physical performance responses during 72 h of military operational stress.
APPLIED SCIENCES
Medicine & Science in Sports & Exercise. 34(11):1814-1822, November 2002.
NINDL, BRADLEY C.; LEONE, CARA D.; J. THARION, WILLIAM; JOHNSON, RICHARD F.; W. CASTELLANI, JOHN; PATTON, JOHN F.; MONTAIN, SCOTT J.
Abstract:
NINDL, B. C., C. D. LEONE, W. THARION, R. F. JOHNSON, J. CASTELLANI, J. F. PATTON, and S. J. MONTAIN. Physical performance responses during 72 h of military operational stress. Med. Sci. Sports Exerc., Vol. 34, No. 11, pp. 1814-1822, 2002.
Purpose: To characterize the impact of prolonged work, underfeeding, and sleep deprivation (i.e., sustained operations; SUSOPS) on physical and occupational related performance during military operational stress.
Methods: Ten male soldiers were tested on days 1 (D1), 3 (D3), and 4 (D4) of a control and an experimental week that included prolonged physical work (total daily energy expenditure ~4500 kcal[middle dot]d-1), underfeeding (~1600 kcal[middle dot]d-1), and sleep deprivation (~2 h[middle dot]d-1). Body composition was measured with dual-energy x-ray absorptiometry (DEXA). Ballistic power was assessed by 30 repetitive squat jumps and bench-press throws. Military-relevant occupational performance was evaluated with a 10-min box lift, obstacle course, grenade throw, rifle marksmanship, and a 25-min wall-build task.
Results: Fat-free mass (-2.3%) and fat mass (-7.3%) declined (P <= 0.05) during SUSOPS. Squat-jump mean power (-9%) and total work (-15%) declined (P <= 0.05) during SUSOPS. Bench-press power output, grenade throw, and marksmanship for pop-up targets were not affected. Obstacle course and box-lift performances were lower (P <= 0.05) on D3 but showed some recovery on D4. Wall building was ~25% lower (P <= 0.05) during SUSOPS.
Conclusion: Decrements in performance during SUSOPS are primarily restricted to tasks that recruit muscles that are over-utilized without adequate recovery. General military skill tasks and occupational physical performance tasks are fairly well maintained.
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Physical performance responses during 72 h of military operational stress.
APPLIED SCIENCES
Medicine & Science in Sports & Exercise. 34(11):1814-1822, November 2002.
NINDL, BRADLEY C.; LEONE, CARA D.; J. THARION, WILLIAM; JOHNSON, RICHARD F.; W. CASTELLANI, JOHN; PATTON, JOHN F.; MONTAIN, SCOTT J.
Abstract:
NINDL, B. C., C. D. LEONE, W. THARION, R. F. JOHNSON, J. CASTELLANI, J. F. PATTON, and S. J. MONTAIN. Physical performance responses during 72 h of military operational stress. Med. Sci. Sports Exerc., Vol. 34, No. 11, pp. 1814-1822, 2002.
Purpose: To characterize the impact of prolonged work, underfeeding, and sleep deprivation (i.e., sustained operations; SUSOPS) on physical and occupational related performance during military operational stress.
Methods: Ten male soldiers were tested on days 1 (D1), 3 (D3), and 4 (D4) of a control and an experimental week that included prolonged physical work (total daily energy expenditure ~4500 kcal[middle dot]d-1), underfeeding (~1600 kcal[middle dot]d-1), and sleep deprivation (~2 h[middle dot]d-1). Body composition was measured with dual-energy x-ray absorptiometry (DEXA). Ballistic power was assessed by 30 repetitive squat jumps and bench-press throws. Military-relevant occupational performance was evaluated with a 10-min box lift, obstacle course, grenade throw, rifle marksmanship, and a 25-min wall-build task.
Results: Fat-free mass (-2.3%) and fat mass (-7.3%) declined (P <= 0.05) during SUSOPS. Squat-jump mean power (-9%) and total work (-15%) declined (P <= 0.05) during SUSOPS. Bench-press power output, grenade throw, and marksmanship for pop-up targets were not affected. Obstacle course and box-lift performances were lower (P <= 0.05) on D3 but showed some recovery on D4. Wall building was ~25% lower (P <= 0.05) during SUSOPS.
Conclusion: Decrements in performance during SUSOPS are primarily restricted to tasks that recruit muscles that are over-utilized without adequate recovery. General military skill tasks and occupational physical performance tasks are fairly well maintained.
Not eating enough makes you lose weight and become weaker? NO WAY!
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bench press and coordination tasks somehow stayed the same though..
"Decrements in performance during SUSOPS are primarily restricted to tasks that recruit muscles that are over-utilized without adequate recovery.".. so maybe they didn't fatigue their chest/tricep muscles too much, and bench didn't go down.
you would think that one would obviously go down with how much lean mass/fat mass/sleep deprivation they lost.
if bench didnt go down and they lost all that mass, they just increased relative strength bigtime ;)
peace
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Circadian variation in sports performance.
Atkinson G, Reilly T.
Centre for Sport and Exercise Sciences, School of Human Sciences, Liverpool John Moores University, England.
Chronobiology is the science concerned with investigations of time-dependent changes in physiological variables. Circadian rhythms refer to variations that recur every 24 hours. Many physiological circadian rhythms at rest are endogenously controlled, and persist when an individual is isolated from environmental fluctuations. Unlike physiological variables, human performance cannot be monitored continuously in order to describe circadian rhythmicity. Experimental studies of the effect of circadian rhythms on performance need to be carefully designed in order to control for serial fatigue effects and to minimise disturbances in sleep. The detection of rhythmicity in performance variables is also highly influenced by the degree of test-retest repeatability of the measuring equipment. The majority of components of sports performance, e.g. flexibility, muscle strength, short term high power output, vary with time of day in a sinusoidal manner and peak in the early evening close to the daily maximum in body temperature. Psychological tests of short term memory, heart rate-based tests of physical fitness, and prolonged submaximal exercise performance carried out in hot conditions show peak times in the morning. Heart rate-based tests of work capacity appear to peak in the morning because the heart rate responses to exercise are minimal at this time of day. Post-lunch declines are evident with performance variables such as muscle strength, especially if measured frequently enough and sequentially within a 24-hour period to cause fatigue in individuals. More research work is needed to ascertain whether performance in tasks demanding fine motor control varies with time of day. Metabolic and respiratory rhythms are flattened when exercise becomes strenuous whilst the body temperature rhythm persists during maximal exercise. Higher work-rates are selected spontaneously in the early evening. At present, it is not known whether time of day influences the responses of a set training regimen (one in which the training stimulus does not vary with time of day) for endurance, strength, or the learning of motor skills. The normal circadian rhythms can be desynchronised following a flight across several time zones or a transfer to nocturnal work shifts. Although athletes show all the symptoms of 'jet lag' (increased fatigue, disturbed sleep and circadian rhythms), more research work is needed to identify the effects of transmeridian travel on the actual performances of elite sports competitors. Such investigations would need to be chronobiological, i.e. monitor performance at several times on several post-flight days, and take into account direction of travel, time of day of competition and the various performance components involved in a particular sport. Shiftwork interferes with participation in competitive sport, although there may be greater opportunities for shiftworkers to train in the hours of daylight for individual sports such as cycling and swimming. Studies should be conducted to ascertain whether shiftwork-mediated rhythm disturbances affect sports performance. Individual differences in performance rhythms are small but significant. Circadian rhythms are larger in amplitude in physically fit individuals than sedentary individuals. Athletes over 50 years of age tend to be higher in 'morningness', habitually scheduling relatively more training in the morning and selecting relatively higher work-rates during exercise compared with young athletes. These differences should be recognised by practitioners concerned with organising the habitual regimens of athletes.
Circadian rhythms in two types of anaerobic cycle leg exercise: force-velocity and 30-s Wingate tests.
Souissi N, Gauthier A, Sesboüé B, Larue J, Davenne D.
Centre de Recherches en Activités Physiques et Sportives UPRES EA 2131, Université de Basse-Normandie, UFR STAPS 14032 Caen Cedex, France.
Previous studies investigating the impact of circadian rhythms on performance during anaerobic cycle leg exercise have yielded conflicting results. The purpose of the present investigation was firstly, to determine the effect of the time of day on anaerobic performance during a force-velocity test on a cycle ergometer (F-V) and the Wingate test and secondly, to relate any changes in anaerobic performance to the circadian rhythm in oral temperature. Nineteen subjects volunteered to take part in the study. In a balanced and randomized study design, subjects were measured for maximal power (P (max)) (force-velocity test), peak power (P (peak)) and mean power (P (mean)) (Wingate test) on six separate occasions. These were at 02 : 00, 06 : 00, 10 : 00, 14 : 00, 18 : 00 and 22 : 00 hours on separate days. There was an interval of 28 h between two successive tests. Oral temperature and body mass were measured before each test. Body mass did not vary during the day but a significant time of day effect was observed for the oral temperature with an acrophase at 18 : 22 +/- 00 : 34 hours. A significant circadian rhythm was found for P (max) with an acrophase at 17 : 10 +/- 00 : 52 hours and an amplitude of 7 %. A time-of-day effect was significant for F (0) and V (0). Also a significant circadian rhythm was observed for P (peak) with an acrophase at 17 : 24 +/- 00 : 36 hours and an amplitude of 7.6 % and for P (mean) with an acrophase at 18 : 00 +/- 01 : 01 hours and an amplitude of 11.3 %. The results indicated that oral temperature, P (peak), P (mean) and P (max) varied concomitantly during the day. These results suggest that there was a circadian rhythm in anaerobic performance during cycle tests. The recording of oral temperature allows one to estimate the time of occurrence of maximal and minimal values in the circadian rhythm of anaerobic performance.
Sports, Sleep, and Circadian Rhythms : Circadian Rhythms and Enhanced Athletic Performance in the National Football League
http://www.journalsleep.org/Articles/200507.pdf
Diurnal Rhythm of the Muscular Performance of Elbow Flexors During Isometric Contractions
The influence of time of day on elbow flexion torque was studied. Thirteen physical education students, 7 males and 6 females, made maximal and submaximal isometric contractions at 90° of elbow flexors using a dynamometer. The torque developed was measured on each contraction. The myoelectric activity of the biceps muscle was also measured at the same time by surface electromyography (EMG) and quantified from the root mean square (RMS) activity. Torque and surface EMGs were measured at 6:00, 9:00, 12:00, 15:00, 18:00, 21:00, and 24:00 h over the same day. Oral temperature before each test session was measured on each occasion after a 30-min rest period. We observed a diurnal rhythm in elbow flexor torque with an acro-phase at 18:00 h and a bathyphase at 6:00 h, in phase with the diurnal rhythm in oral temperature. However, the diurnal rhythm of temperature did not appear to have any influence on the torque. Links between neuromuscular efficiency and RMS/torque ratio were evaluated by measuring muscle activity along with torque. We also assessed variations in the level of maximal activity of the muscle under maximal voluntary contraction. Neuromuscular efficiency fluctuated during the day, with maximal and minimal efficiency at 18:00 h and 9:00 h, respectively, whereas activation level was maximal at 18:00 h and minimal at 9:00 h. The diurnal rhythm of torque was accounted for by variations in both central nervous system command and the contractile state of the muscle.
Circadian performance differences between morning and evening 'types'
Two groups of subjects identified as either morning (M) or evening (E) types, determined by a self-assessment questionnaire, were measured for performance efficiency at a simulated production-line inspection task given for 15 sessions at different times of the waking day. Systematic fatigue and practice effects were minimised by a random presentation of these sessions over a series of days. Although there were no significant within- or between-group changes with circadian trends for items erroneously rejected, significant differences were apparent with the number of items correctly rejected. M types' correct rejection levels were significantly better than E types' in the morning, whereas they were worse during the evening. Whilst E types showed a steady improvement throughout the day, M types showed a general decline. A post-lunch dip in performance was quite evident for M types, but not for E types. In addition, the circadian trends in correct rejection levels and body temperature were highly positively correlated for E types, but a significant negative relationship between these parameters was found for M types. These findings are discussed.
CIRCADIAN RHYTHMS IN HUMAN MUSCULAR EFFICIENCY: CONTINUOUS PHYSICAL EXERCISE VERSUS CONTINUOUS REST. A CROSSOVER STUDY
This study deals with the influence of time of day on neuromuscular efficiency in competitive cyclists during continuous exercise versus continuous rest. Knee extension torque was measured in ultradistance cyclists over a 24h period (13:00 to 13:00 the next day) in the laboratory. The subjects were requested to maintain a constant speed (set at 70% of their maximal aerobic speed obtained during a preliminary test) on their own bicycles, which were equipped with cyclosimulators. Every 4h, torque developed and myoelectric activity were estimated during maximal isometric voluntary contractions of knee extensors using an isokinetic dynamometer. Mesenteric temperature was monitored by telemetry. The same measures were also recorded while the subjects were resting awake until 13:00 the next day. During activity, torque changed within the 24h period (p < .005), with an acrophase at 19:10 and an amplitude of 7.8% around the mean of 70.7%. At rest, a circadian rhythm was observed in knee extensor torque (p < .05), with an acrophase at 19:30 and an amplitude of 6% around the mean of 92.3%. Despite the standardized conditions, the results showed that isometric maximal strength varied with time of day during both a submaximal exercise and at rest without prior exercise. The sine waves representing these two rhythms were correlated significantly. Although at rest the diurnal rhythm followed muscular activity (i.e., neurophysiological factors), during exercise, this rhythm was thought to stem more from fluctuations in the contractile state of muscle. (Chronobiology International, 17(5), 693-704, 2000)
Circadian rhythms have no effect on cycling performance
The aim of this research was to determine if circadian rhythms have an effect on time trial cycling performance of 15 min duration. Seven males (Mean±SD) : age, 22.3±4.9yr ; height 179.0±7.9cm, body mass 74.5±15.5 kg; VO2max 68.0 ± 5.7 ml x kg-1 x min-1 who were all competitive cyclists or triathletes with previous experience in laboratory testing procedures volunteered to participate in this study. Each of the seven subjects underwent a series of four tests; one VO2 max test, and three 15 min maximal performance tests, at varying times during a 24hr period. Testing times were at 08.00-10.00; 14.00-16.00 and 20.00-22.00 hours. Heart rate was recorded during the last 10-15 seconds of each minute and blood lactate levels were taken at 5 and 10 min during exercise and again immediately post-exercise. O2 consumption was measured continuously using open circuit spirometry. RPE was measured using the Borg scale at 5 and 10 min during, and again immediately following the completion of testing. Resting oral temperature was the only variable to show a significant time of day effect (p<0.05). Oral temperature during the afternoon was higher than both morning and evening results by 0.76°C and 0.09°C respectively. Total work (kJ) and average power output (W) were recorded at their highest during the morning session and reached a trough during the afternoon session, but these differences were not significant (p =0.9997 and 0.9972 respectively). The results obtained in this study indicate that while certain biological rhythms are present, they appear to have no effect on this type of cycling performance. Although athletic performance may be enhanced by training programs that are compatible with an individuals body clock, the ability to perform and train at various times has an adaptive response which appears to over-ride these naturally inherent rhythms.
Time-of-day dependence of isokinetic leg strength and associated interday variability.
J P Wyse, T H Mercer and N P Gleeson
Division of Sport, Health and Exercise, School of Sciences, Staffordshire University, Stoke-on-Trent, UK.
The purpose of this study was to assess the interday variability and time-of-day effects on selected isokinetic leg strength indices. Nine adult collegiate sportsmen (mean(s.e.) age 19.6(0.5) years; mean(s.e.) height 1.81(0.02) m; mean(s.e.) body mass 76.5(3.1) kg) completed a series of nine test sessions, organized so that each subject was tested three times within a day (08.00-09.00 hours; 13.00-14.00 hours; 18.00-19.30 hours), on three occasions, each separated by a minimum of 7 days. Gravity-corrected indices of extension peak torque (EPT), flexion peak torque (FPT), and the peak torque ratio (PTR), at contraction velocities of 1.05 rad s-1 and 3.14 rad s-1, were calculated for each subject using an isokinetic dynamometer. Two-way repeated measures analysis of variance of coefficient of variation (V%) scores revealed no significant differences in performance variability across within-subject factors of time-of-day and performance index (P > 0.05). Overall mean(s.e.) V% for scores across experimental conditions were 3.97(0.72)% at 1.05 rad s-1 and 5.98(1.23)% at 3.14 rad s-1, suggesting that similar levels of measurement error occur between 08.00-19.30 hours. One-way repeated measures analysis of variance of absolute strength indices (EPT, FPT and PTR) revealed that significantly higher scores were achieved during session 3 (18.00-19.30 hours), with mean(s.e.) values of 249.1(40.0) N m, 149.0(32.3) N m, 59.5(5.0)% at 1.05 rad s-1, and 172.1(38.7) N m, 121.3(27.7) N m, 71.1(6.2)% at 3.14 rad s-1, respectively (P < 0.05). This finding appears to be consistent with current knowledge about time-of-day effects on the assessment of muscular strength. Thus for stable and maximal values to be obtained during isokinetic leg testing, the use of multiple-trial protocols is recommended, with testing occurring as close to 18.00-19.30 hours as possible. In addition, the observed significant time-of-day effect suggests that appropriate comparison of maximal isokinetic leg strength can only be achieved based on data obtained within 30 min of the same time of day.
Effects of one night's sleep deprivation on anaerobic performance the following day
The purpose of this study was to determine the effect of one night's sleep deprivation on anaerobic performance in the morning and afternoon of the following day. Thirteen healthy males were studied twice in a balanced, randomized design. The experiment consisted of two conditions 1 week apart. In the sleep deprivation condition (SDN) subjects remained awake overnight and in the control condition (reference night, RN) the same subjects slept at home, retiring between 2230 and 2330 hours, as decided individually, and rising at 0500 hours. In both conditions, activity, sleep and diet were monitored by actimetry and daily activity and dietary diaries. Physical performance testing was carried out at 0600 hours and at 1800 hours after the one night of sleep and the one night of sleep deprivation. At each test occasion, subjects were measured for maximal power (P max), peak power (P peak) and mean power (P mean). Blood lactate concentrations were measured at rest, at the end of the force–velocity (F–V) test, just before and just after the Wingate test and again 5 min later. Oral temperatures were measured every 2 h. In both conditions, the results showed a circadian rhythm in temperature. Analysis of variance revealed a significant (sleep × time of day of test) interaction effect on P peak, P mean and P max. These variables improved significantly from morning to afternoon after RN and SDN. The reference night was followed by a greater improvement than the SDN. Up to 24 h of waking, anaerobic power variables were not affected; however, they were impaired after 36 h without sleep. Analysis of variance revealed that blood lactate concentrations were unaffected by sleep loss, by time of day of testing or by the interaction of the two. In conclusion, sleep deprivation reduced the difference between morning and afternoon in anaerobic power variables. Anaerobic performances were unaffected after 24 h of wakefulness but were impaired after 36 h without sleep.
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Effects of dehydration on isometric muscular strength and endurance.
Applied Sciences
Medicine & Science in Sports & Exercise. 30(2):284-288, February 1998.
GREIWE, JEFFREY S.; STAFFEY, KIMBERLY S.; MELROSE, DONALD R.; NARVE, MURIEL D.; KNOWLTON, RONALD G.
Abstract:
To examine the effects of rapid dehydration on isometric muscular strength and endurance, seven men were tested at baseline (control) and after a dehydration (dHST) and a euhydration (eHST) heat stress trial. The dHST consisted of intermittent sauna exposure until 4% of body mass was lost, whereas the eHST consisted of intermittent sauna exposure (same duration as dHST) with water replacement. Peak torque was determined for the knee extensors and elbow flexors during three isometric maximal voluntary contractions. Time to fatigue was determined by holding a maximal voluntary contraction until torque dropped below 50% peak torque for 5 s. Strength and endurance were assessed 3.5 h after the HSTs (no food or water intake). Body mass was decreased 3.8 +/- 0.4% post dHST and 0.4 +/- 0.3% post eHST. Plasma volume was decreased 7.5 +/- 4.6% and 5.7 +/- 4.4%, 60 and 120 min post dHST, respectively. A small (1.6 mEq[middle dot]L-1) but significant increase was found for serum Na+ concentration 60 min post dHST but had returned to predehydration level 120 min post dHST. Serum K+ and myoglobin concentrations were not affected by HSTs. Peak torque was not different (P > 0.05) among control, dHST, and eHST for the knee extensors (Mean (Nm) +/- SD, 285 +/- 79, 311 +/- 113, and 297 +/- 79) and elbow flexors (79 +/- 12, 83 +/- 15, and 80+/- 12). Time to fatigue was not different (P > 0.05) among control, dHST and eHST for the knee extensors (Mean (s) +/- SD, 42.4+/- 11.5, 45.3 +/- 7.6, and 41.8 +/- 6.0) and elbow flexors(48.2 +/- 8.9, 44.0 +/- 9.4, and 46.0 +/- 6.4). These results provide evidence that isometric strength and endurance are unaffected 3.5 h after dehydration of approximately 4% body mass.
Sleep deprivation induced anxiety and anaerobic performance
The aim of this study was to investigate the effects of sleep
deprivation induced anxiety on anaerobic performance. Thirteen
volunteer male physical education students completed the Turk-
ish version of State Anxiety Inventory and performed Wingate
anaerobic test for three times: (1) following a full-night of habit-
ual sleep (baseline measurements), (2) following 30 hours of
sleep deprivation, and (3) following partial-night sleep depriva-
tion. Baseline measurements were performed the day before
total sleep deprivation. Measurements following partial sleep
deprivation were made 2 weeks later than total sleep deprivation
measurements. State anxiety was measured prior to each Win-
gate test. The mean state anxiety following total sleep depriva-
tion was higher than the baseline measurement (44.9 ± 12.9 vs.
27.6 ± 4.2, respectively, p = 0.02) whereas anaerobic perform-
ance parameters remained unchanged. Neither anaerobic pa-
rameters nor state anxiety levels were affected by one night
partial sleep deprivation. Our results suggest that 30 hours con-
tinuous wakefulness may increase anxiety level without impair-
ing anaerobic performance, whereas one night of partial sleep
deprivation was ineffective on both state anxiety and anaerobic
performance.
The role of a short post-lunch nap in improving cognitive, motor, and sprint performance in participants with partial sleep deprivation
The aim of this study was to determine the effects of a post-lunch nap on subjective alertness and performance following partial sleep loss. Ten healthy males (mean age 23.3 years, s = 3.4) either napped or sat quietly from 13:00 to 13:30 h after a night of shortened sleep (sleep 23:00 - 03:00 h only). Thirty minutes after the afternoon nap or control (no-nap) condition, alertness, short-term memory, intra-aural temperature, heart rate, choice reaction time, grip strength, and times for 2-m and 20-m sprints were recorded. The afternoon nap lowered heart rate and intra-aural temperature. Alertness, sleepiness, short-term memory, and accuracy at the 8-choice reaction time test were improved by napping (P < 0.05), but mean reaction times and grip strength were not affected (P > 0.05). Sprint times were improved. Mean time for the 2-m sprints fell from 1.060 s (s(x)macr = 0.018) to 1.019 s (s(x)macr = 0.019) (P = 0.031 paired t-test); mean time for the 20-m sprints fell from 3.971 s (s(x)macr = 0.054) to 3.878 s (s(x)macr = 0.047) (P = 0.013). These results indicate that a post-lunch nap improves alertness and aspects of mental and physical performance following partial sleep loss, and have implications for athletes with restricted sleep during training or before competition.
Effects of One Night of Partial Sleep Deprivation upon Diurnal Rhythms of Accuracy and Consistency in Throwing Darts
Authors: Benjamin J. Edwards a; Jim Waterhouse a
Affiliation: a Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK
DOI: 10.1080/07420520902929037
Publication Frequency: 8 issues per year
Published in: journal Chronobiology International, Volume 26, Issue 4 May 2009 , pages 756 - 768
Subjects: Biological Rhythms; Physiology;
Formats available: HTML (English) : PDF (English)
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Abstract
Sixty subjects were tested five times per waking day on two occasions for accuracy and reliability in throwing 20 darts at a target. Two experimental conditions were investigated: following a normal nocturnal sleep (7-8 h sleep, normal) and after having retired to bed 4 h later than normal the previous night but rising at the normal time (3-4 h sleep, sleep deprivation). Sublingual (core) temperature and subjective estimates of alertness and fatigue were measured in all sessions. Performance at throwing darts was assessed by three methods: mean distance of the dart from the bulls-eye; number of times the target was missed; and variability of the scores from the darts thrown. There was no evidence that performance was affected by physical fatigue arising during the course of throwing the 20 darts. All variables showed significant diurnal rhythms, those of alertness and performance being phased over 1 h earlier than core temperature, and that of fatigue over 1 h earlier than the inverse of temperature. Core temperature was not affected by sleep deprivation, but all other variables showed significant changes, indicative of mood and performance decrement. Increasing time awake was associated with decreased alertness and increased fatigue, as well as slight negative effects upon performance. We conclude that the simple task of throwing darts at a target provides information about chronobiological changes in circumstances where time awake and sleep loss might affect psychomotor performance.
Keywords: Circadian rhythms; Psychomotor performance; Time awake
Effects of a selective sleep deprivation on subsequent anaerobic performance
The aim of the study was to investigate the effects of a partial sleep deprivation on a subsequent supramaximal exercise evaluated from the 30 second Wingate test, and on the following recovery. To take into account the active muscle mass, the Wingate test was performed against a constant braking force related to the data of a force-velocity test conducted on a Monark cycle ergometer (Model 814 E with weights) one week before the experimental test. Eight highly trained athletes were enrolled for this study. The changes in ventilatory and metabolic responses were analyzed during and upon completion of physical 30 second exercise, taking place after two nights, in other words, after a reference night and after a night with reduced sleep. Partial sleep deprivation was obtained by delaying bedtime until 3 a.m. The 30 second Wingate test was performed between 9 a.m. and noon the following days, using a Monark ergometer (Model 814 E). The analyses of change scores disclosed that there were no main significant effects for measures of ventilation, lactates and pHV levels under the two experimental conditions. The peak power, the mean power output and the peak velocity recorded after partial sleep deprivation were not modified in comparison with the values obtained after the reference night. These findings suggest that acute sleep loss did not contribute to alterations in supramaximal exercise.
Sleep deprivation and exercise
Sleep deprivation can be defined as total or partial suppress of sleep and is associated with alterations in endocrine, metabolic, physical, cognitive functions and modifications of the sleep patterns that compromise health and quality of life. Physical exercise is associated with improvement of cardiovascular, respiratory, muscular, endocrine and nervous system, and a better sleep quality. However, the association of these two conditions is unclear, partly due to the difficulty to obtain volunteers to participate in this type of protocol with no financial compensation. The majority of the studies which investigate the association between physical exercises and sleep deprivation focus on aerobic performance and verify little or no effect of this parameter. Concerning anaerobic power and strength, significant alterations have not been found; however, for prolonged events there may be an interaction between these two factors, which suggests a protection mechanism. Nevertheless, it is important to consider that one of the main alterations caused by sleep deprivation the increase of the subjective perception, which presents a factor to decrease and compromise the physical performance per se, and may represent a masking element of the deleterious effects of sleep deprivation. Thus, the aim of present review is to discuss the different aspects of relationship between physical exercise and sleep deprivation, showing their effects and consequences in physical performance.
The Impact of Sleep Deprivation on Decision Making: A Review
Few sleep deprivation (SD) studies involve realism or high-level decision making, factors relevant to
managers, military commanders, and so forth, who are undergoing prolonged work during crises. Instead,
research has favored simple tasks sensitive to SD mostly because of their dull monotony. In contrast,
complex rule-based, convergent, and logical tasks ate unaffected by short-term SD, seemingly because
of heightened participant interest and compensatory effort. However, recent findings show that despite
this effort, SD still impairs decision making involving the unexpected, innovation, revising plans,
competing distraction, and effective communication. Decision-making models developed outside SD
provide useful perspectives on these latter effects, as does a neuropsychological explanation of sleep
function. SD presents particular difficulties for sleep-deprived decision makers who require these latter
skills during emergency situations.
The Acute Effects of Twenty-Four Hours of Sleep Loss on the Performance of National-Caliber Male Collegiate Weightlifters
Blumert, P.A., A.J. Crum, M. Ernsting, J.S. Volek, D.B. Hollander, E.E. Haff, and G.G. Haff. The acute effects of twenty-four hours of sleep loss on the performance of national-caliber male collegiate weightlifters. J. Strength Cond. Res. 21(4):1146–1154. 2007.—Currently, the degree to which sleep loss influences weightlifting performance is unknown. This study compared the effects of 24 hours of sleep loss on weightlifting performance and subjective ratings of psychological states pre-exercise and postexercise in national-caliber male collegiate weightlifters. Nine males performed a maximal weightlifting protocol following 24 hours of sleep loss and a night of normal sleep. The subjects participated in a randomized, counterbalanced design with each sleep condition separated by 7 days. Testosterone and cortisol levels were quantified prior to, immediately after, and 1 hour after the resistance training session. Additionally, profile of mood states and subjective sleepiness were evaluated at the same time points. The resistance training protocol consisted of several sets of snatches, clean and jerks, and front squats. Performance was evaluated as individual exercise volume load, training intensity and overall workout volume load, and training intensity. During each training session the maximum weight lifted for the snatch, clean and jerk, and front squat were noted. No significant differences were found for any of the performance variables. A significant decrease following the sleep condition was noted for cortisol concentration immediately after and 1 hour postexercise. Vigor, fatigue, confusion, total mood disturbance, and sleepiness were all significantly altered by sleep loss. These data suggest that 24 hours of sleep loss has no adverse effects on weightlifting performance. If an athlete is in an acute period of sleep loss, as noticed by negative mood disturbances, it may be more beneficial to focus on the psychological (motivation) rather than the physiological aspect of the sport.
Caffeine: Implications for Alertness in Athletes
Caffeine is one of the most widely consumed drugs in the world, taken socially and for its alertness- and performance-promoting actions. Extensive reports assert that caffeine increases alertness and cognitive performance levels and, when taken before exercise, demonstrates ergogenic properties. Caffeine ingestion has been associated with increased performance during endurance submaximal, and acute, high-intensity exercise. The exact mechanism of action for the performance effects of caffeine is unknown, although several physiologically and psychologically based theories exist as to how caffeine achieves increased performance capabilities. This paper outlines the known sites of caffeine activity in the body,and discusses these with respect to the effects of caffeine observed during performance assessments.
Effect of sleep deprivation on tolerance of prolonged exercise
Summary Acute loss of sleep produces few apparent physiological effects at rest. Nevertheless, many anecdotes suggest that adequate sleep is essential for optimum endurance athletic performance. To investigate this question, heavy exercise performance after 36 h without sleep was compared with that after normal sleep in eight subjects. During prolonged treadmill walking at about 80% of the $$\dot V_{O_2 } $$ max, sleep loss reduced work time to exhaustion by an average of 11% (p=0.05). This decrease occurred despite doubling monetary incentives for subjects during work after sleeplessness. Subjects appeared to fall into “resistant” and “susceptible” categories: four showed less than a 5% change in performance after sleep loss, while four others showed decrements in exercise tolerance ranging from 15 to 40%. During the walk, sleep loss resulted in significantly greater perceived exertion (p<0.05), even though exercise heart rate and metabolic rate ( $$\dot V_{O_2 } $$ and $$\dot V_{CO_2 } $$ ) were unchanged. Minute ventilation was significantly elevated during exercise after sleep loss (p<0.05). Sleep loss failed to alter the continuous slow rises in $$\dot V_E $$ E and heart rate that occurred as work was prolonged. These findings suggest that the psychological effects of acute sleep loss may contribute to decreased tolerance of prolonged heavy exercise.
Sleep deprivation and cardiorespiratory function
Influence of intermittent submaximal exercise
Journal European Journal of Applied Physiology and Occupational Physiology
Publisher Springer Berlin / Heidelberg
ISSN 0301-5548 (Print) 1439-6327 (Online)
Issue Volume 56, Number 3 / May, 1987
DOI 10.1007/BF00690902
Pages 338-344
SpringerLink Date Sunday, December 12, 2004
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Sleep deprivation and cardiorespiratory function
Influence of intermittent submaximal exercise
M. J. Plyley1, R. J. Shephard1 Contact Information, G. M. Davis1 and R. C. Goode1
(1) School of Physical and Health Education, University of Toronto, M5S 1A1 Toronto, Ontario, Canada
Accepted: 24 November 1986
Summary The effects of 64 h of sleep deprivation upon cardiorespiratory function was studied in 11 young men ( $$\dot V_{{\text{O}}_{{\text{ 2 max}}} } = 55.5{\text{ ml kg}}^{ - 1} {\text{ min}}^{ - 1} ,{\text{ STPD}}$$ ). Six subjects engaged in normal sedentary activities, while the others walked on a treadmill at 28% $$\dot V_{{\text{O}}_{{\text{ 2 max}}} } $$ for one hour in every three; eight weeks later, sleep deprivation was repeated with a crossover of subjects. Immediate post-deprivation measurement of $$\dot V_{{\text{O}}_{{\text{ 2 max}}} } $$ showed a small but statistically significant decrease (–3.8 ml min–1 kg–1, STPD), with no difference between exercise and control trials. The final decrement in aerobic power was not due to a loss of motivation, as 88% (21 of 24) of post-deprivation tests still showed a plateau of $$\dot V_{{\text{O}}_{{\text{ 2 max}}} } $$ ; in addition, terminal heart rates (198 vs 195 beats min–1), respiratory exchange ratios (1.14 vs 1.15) and blood lactate levels (12.1 vs 11.8 mmol l–1) were not significantly different after sleep deprivation. The decrease in $$\dot V_{{\text{O}}_{{\text{ 2 max}}} } $$ was associated with a lower $$\dot V_{{\text{E}}_{{\text{ 2 max}}} } $$ (127 vs 142 l min–1, BTPS) and a substantial haemodilution (13%). Physiological responses to sub-maximal exercise showed persistence of the normal diurnal rhythm in heart rate and oxygen consumption, with no added effects due to sleep deprivation. However, ratings of perceived exertion (Borg scale) increased significantly throughout sleep deprivation. The findings are consistent with a mild respiratory acidosis, secondary to reduced cortical arousal and/or a progressive depletion of tissue glycogen stores which are not altered appreciably by moderate physical activity.
Multiple Effects of Caffeine on Simulated High-Intensity Team-Sport Performance.
Applied Sciences
Medicine & Science in Sports & Exercise. 37(11):1998-2005, November 2005.
STUART, GENE R. 1; HOPKINS, WILL G. 1; COOK, CHRISTIAN 2; CAIRNS, SIMEON P. 1
Abstract:
Introduction: Caffeine enhances performance of single bouts of endurance exercise, but its effects on repeated bouts typical of those in high-intensity team sports are unclear.
Purpose: To investigate effects of caffeine in a performance test simulating physical and skill demands of a rugby union game.
Methods: The study was a double-blind, randomized, crossover design in which nine competitive male rugby players ingested either caffeine (6 mg[middle dot]kg-1 body mass) or placebo (dextrose) 70 min before performing a rugby test. Each test consisted of seven circuits in each of two 40-min halves with a 10-min half-time rest. Each circuit included stations for measurement of sprint time (two straight-line and three agility sprints), power generation in two consecutive drives, and accuracy for passing balls rapidly. Interstitial fluid was sampled transdermally by electrosonophoresis before ingestion of caffeine or placebo and then before testing, at half-time, and immediately after testing; samples were assayed chromatographically for caffeine and epinephrine concentrations.
Results: The effects of caffeine on mean performance (+/-90% confidence limits) over all 14 circuits were: sprint speeds, 0.5% (+/-1.7%) through 2.9% (+/-1.3%); first-drive power, 5.0% (+/-2.5%); second-drive power, -1.2% (+/-6.8%); and passing accuracy, 9.6% (+/-6.1%). The enhancements were mediated partly through a reduction of fatigue that developed throughout the test and partly by enhanced performance for some measures from the first circuit. Caffeine produced a 51% (+/-11%) increase in mean epinephrine concentration; correlations between individual changes in epinephrine concentration and changes in performance were mostly unclear, but there were some strong positive correlations with sprint speeds and a strong negative correlation with passing accuracy.
Conclusion: Caffeine is likely to produce substantial enhancement of several aspects of high-intensity team-sport performance.
Elevations in core and muscle temperature impairs repeated sprint performance
B. Drust 1 , P. Rasmussen 2 , M. Mohr 2 , B. Nielsen 2 and L. Nybo 2
1 Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, UK
2 Institute of Exercise and Sport Sciences, August Krogh Institute, University of Copenhagen, Copenhagen, Denmark
Correspondence to B Drust, Research Institute for Sport and Exercise Sciences, Liverpool John Moores University, Henry Cotton Campus, Webster Street, Liverpool L3 2ET, UK.
Copyright 2005 Scandinavian Physiological Society
KEYWORDS
fatigue • hyperthermia • muscle metabolites • sprint performance
Abstract
Abstract Methods Results Discussion References
Aim: The present study investigated the effects of hyperthermia on intermittent exercise and repeated sprint performance.
Methods: Seven men completed 40 min of intermittent cycling comprising of 15 s exercise (306 ± 22 W) and 15 s rest periods (0 W) followed by 5 × 15 s maximal sprints on a cycle ergometer in normal (?20 °C, control) and hot (40 °C, hyperthermia) environments.
Results: Completion of the intermittent protocol in the heat elevated core and muscle temperatures (39.5 ± 0.2 °C; 40.2 ± 0.4 °C), heart rate (178 ± 11 beats min?1), rating of perceived exertion (RPE) (18 ± 1) and noradrenaline (38.9 ± 13.2 ?mol l?1) (all P < 0.05). During the first sprint (n = 6), both peak and mean power output were similar across the environmental conditions. However, mean power over the last four sprints declined to a larger extent during hyperthermia compared with the control trial (P < 0.05). Consequently, average mean power output during the five sprints was lower in hyperthermia (558.0 ± 146.9 W) compared with control (617.5 ± 122.6 W; P < 0.05). Power output during the repeated sprints was reduced by hyperthermia despite an elevated muscle temperature that should promote sprint performance. Venous plasma potassium concentrations (H; 5.3 ± 0.8 mmol l?1 vs. C; 6.3 ± 1.0 mmol l?1, P = 0.06) and muscle lactate levels (H; 76.6 ± 24.3 mmol kg?1 dry weight vs. C; 108.8 ± 20.1 mmol kg?1 dry weight) were lower following the hyperthermic sprints compared to control.
Conclusion: Although an elevated muscle temperature is expected to promote sprint performance, power output during the repeated sprints was reduced by hyperthermia. The impaired performance does not seem to relate to the accumulation of recognized metabolic fatigue agents and we, therefore, suggest that it may relate to the influence of high core temperature on the function of the central nervous system.
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Polyphasic sleep strategies improve prolonged sustained performance: A field study on 99 sailors
Author: Claudio Stampiab
Affiliations: a Human Neurosciences Research Unit, University of Ottawa, Ottawa, Canada
b University of Bologna, Italy
DOI: 10.1080/02678378908256879
Publication Frequency: 4 issues per year
Published in: journal Work & Stress, Volume 3, Issue 1 January 1989 , pages 41 - 55
Subjects: Behavioral Medicine; Health Psychology; Occupational/Industrial Health & Safety; Office & Workplace; Work & Organizational Psychology;
Formats available: PDF (English)
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Abstract
In situations where continuous prolonged work demands exist, the habitual nocturnal monophasic (6-8h duration) sleep pattern can rarely be accomplished, and performance effectiveness may sometimes be severely compromised by accumulation of sleep debt. Several studies have shown that naps can be disproportionately effective in recovering functioning during continuous work (CW).
In this study, sleep-wake patterns and their relationship to performance were studied for 99 sailors involved in solo and double-handed ocean sailing races (a model of a highly demanding CW situation). Most sailors spontaneously adopted multiple nap sleep-wake schedules and adapted without major difficulties to such polyphasic patterns. 66.5% had mean sleep episode durations (SEDs) ranging from 20 min to 2h. Overall mean Total Sleep Time (TST) per 24h was reduced from a baseline of 7.5 to 6.3h. Race performance correlated negatively and significantly with mean SEDs and TSTs. Best performance results were obtained by those sleeping for periods of between 20 min and 1 h and for a total of 4.5 to 5.5h of sleep per day.
The results are discussed together with several chronobiological, phylogenetic and experimental studies and issues, all of which suggest that adult humans may have a damped polyphasic sleep-wake tendency. It is also proposed that polyphasic sleep schedules could become promising and feasible solutions for the management of sleep requirements under prolonged CW situations.
Truck Drivers Sleep-Wake Time Arrangements
Authors: C. R. C. Moreno; L. Matuzaki; F. Carvalho; R. Alves; I. Pasqua; G. Lorenzi-Filho
DOI: 10.1076/brhm.34.2.137.14487
Publication Frequency: 6 issues per year
Published in: journal Biological Rhythm Research, Volume 34, Issue 2 April 2003 , pages 137 - 143
Subjects: Animal Physiology; Biological Rhythms; Biology; Physiology;
Formats available: PDF (English)
Previously published as: Journal of Interdisiplinary Cycle Research (0022-1945) until 1994
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Abstract
Irregular working hours, including night work, change sleep-wake time arrangements which in turn might affect the ability to drive safely. This study aims to compare the effects of an irregular and a fixed day shift system on the sleep-wake cycle of truck drivers. The investigation of sleep-wake cycle was carried-out with 37 truck drivers working on two transportation plants: 24 working on irregular working hours and 13 on fixed day shift. The truck drivers filled out sleep logs and wore actigraphs for 10 consecutive days to identify activity and rest episodes. The group working in irregular hours showed more sleep episodes per 24 h and they were shorter compared to the fixed shift group (p < 0.05). No differences were found between the two transportation plants. These results suggest an the influence of working hours on specific sleep-wake patterns. The polyphasic sleep pattern shown by irregular shift group could be a strategy to cope with sleep deprivation, which may account for their difficulty to resist falling asleep behind the wheel.
Sleep Inertia: Best Time Not to Wake Up?
Authors: Paul Naitoha; Tamsin Kellya; Harvey Babkoffb
Affiliations: a Naval Health Research Center, San Diego, California, USA
b Department of Psychology, Bar-Ilan University, Ramat-Gan, Israel
DOI: 10.3109/07420529309059699
Publication Frequency: 8 issues per year
Published in: journal Chronobiology International, Volume 10, Issue 2 April 1993 , pages 109 - 118
Subjects: Biological Rhythms; Physiology;
Formats available: PDF (English)
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Abstract
Sleep inertia is a brief period of inferior task performance and/or disori-entation immediately after sudden awakening from sleep. Normally sleep inertia lasts <5 min and has no serious impact on conducting routine jobs. This preliminary study examined whether there are best and worst times to wake up stemming from circadian effects on sleep inertia. Since the process of falling asleep is strongly influenced by circadian time, the reverse process of awakening could be similarly affected. A group of nine subjects stayed awake for a 64-h continuous work period, except for 20-min sleep periods (naps) every 6 h. Another group of 10 subjects stayed awake for 64 h without any sleep. The differences between these two groups in performance degradation are expected to show sleep inertia on the background of sleep deprivation. Sleep inertia was measured with Baddeley's logical reasoning task, which started within 1 min of awakening and lasted for 5 min. There appeared to be no specific circadian time when sleep inertia is either maximal or minimal. An extreme form of sleep inertia was observed, when the process of waking up during the period of the circadian body temperature trough became so traumatic that it created “sleep (nap) aversion.” The findings lead to the conclusion that there are no advantages realized on sleep inertia by waking up from sleep at specific times of day.
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http://onlinelibrary.wiley.com/doi/10.1111/cen.12747/full
Metabolic and hormonal effects of ‘catch-up’ sleep in men with chronic, repetitive, lifestyle-driven sleep restriction
"Results
Insulin sensitivity was higher following three nights of sleep extension compared to sustained sleep restriction. Fasting insulin, c-peptide, HOMA-IR, HOMA-β, leptin and PYY decreased with ‘catch-up’ sleep, QUICKI and testosterone increased, while morning cortisol and LH did not change. Targeted acoustic stimuli reduced SWS by 23%, but did not alter insulin sensitivity.
Conclusions
Three nights of ‘catch-up’ sleep improved insulin sensitivity in men with chronic, repetitive sleep restriction. Methods to improve metabolic health by optimizing sleep are plausible."
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oh that's really interesting. thanks gukl.