Breakdown of high-energy phosphate compounds and lactate accumulation during short supramaximal exercise



Summary  Muscle ATP, creatine phosphate and lactate, and blood pH and lactate were measured in 7 male sprinters before and after running 40, 60, 80 and 100 m at maximal speed. The sprinters were divided into two groups, group 1 being sprinters who achieved a higher maximal speed (10.07±0.13 m ·s–1) than group 2 (9.75±0.10 m ·s–1), and who also maintained the speed for a longer time. The breakdown of high-energy phosphate stores was significantly greater for group 1 than for group 2 for all distances other than 100 m; the breakdown of creatine phosphate for group 1 was almost the same for 40 m as for 100 m. Muscle and blood lactate began to accumulate during the 40 m exercise. The accumulation of blood lactate was linear (0.55±0.02 mmol · s–1 ·1–1) for all distances, and there were no differences between the groups. With 100 m sprints the end-levels of blood and muscle lactate were not high enough and the change in blood pH was not great enough for one to accept that lactate accumulation is responsible for the decrease in running speed over this distance.

We concluded that 1) in short-term maximal exercise, performance depends on the capacity for using high-energy phosphates at the beginning of the exercise, and 2) the decrease in running speed begins when the high-energy phosphate stores are depleted and most of the energy must then be produced by glycolysis.





Neural Influences on Sprint Running: Training Adaptations and Acute Responses.

Review Article
Sports Medicine. 31(6):409-425, 2001.
Ross, Angus; Leveritt, Michael; Riek, Stephan

Abstract:
Performance in sprint exercise is determined by the ability to accelerate, the magnitude of maximal velocity and the ability to maintain velocity against the onset of fatigue. These factors are strongly influenced by metabolic and anthropometric components. Improved temporal sequencing of muscle activation and/or improved fast twitch fibre recruitment may contribute to superior sprint performance. Speed of impulse transmission along the motor axon may also have implications on sprint performance. Nerve conduction velocity (NCV) has been shown to increase in response to a period of sprint training. However, it is difficult to determine if increased NCV is likely to contribute to improved sprint performance.

An increase in motoneuron excitability, as measured by the Hoffman reflex (H-reflex), has been reported to produce a more powerful muscular contraction, hence maximising motoneuron excitability would be expected to benefit sprint performance. Motoneuron excitability can be raised acutely by an appropriate stimulus with obvious implications for sprint performance. However, at rest H-reflex has been reported to be lower in athletes trained for explosive events compared with endurance-trained athletes. This may be caused by the relatively high, fast twitch fibre percentage and the consequent high activation thresholds of such motor units in power-trained populations. In contrast, stretch reflexes appear to be enhanced in sprint athletes possibly because of increased muscle spindle sensitivity as a result of sprint training. With muscle in a contracted state, however, there is evidence to suggest greater reflex potentiation among both sprint and resistance-trained populations compared with controls. Again this may be indicative of the predominant types of motor units in these populations, but may also mean an enhanced reflex contribution to force production during running in sprint-trained athletes.

Fatigue of neural origin both during and following sprint exercise has implications with respect to optimising training frequency and volume. Research suggests athletes are unable to maintain maximal firing frequencies for the full duration of, for example, a 100m sprint. Fatigue after a single training session may also have a neural manifestation with some athletes unable to voluntarily fully activate muscle or experiencing stretch reflex inhibition after heavy training. This may occur in conjunction with muscle damage.

The optimal downhill slope for acute overspeed running. (2008)

PURPOSE: This study evaluated a variety of downhill slopes in an effort to determine the optimal slope for overspeed running. METHODS: Thirteen NCAA Division III college athletes who participated in soccer, track, and football ran 40-yd (36.6-m) sprints, on downhill slopes of 2.1 degrees , 3.3 degrees , 4.7 degrees , 5.8 degrees , and 6.9 degrees in random order. All sprints were timed using the Brower Timing System Speedtrap II. Data were analyzed with SSPS 15.0. A 1-way repeated-measures analysis of variance revealed significant main effects for the test slopes (P = .000). Bonferroni-adjusted pairwise comparisons determined that there were a number of differences between the hill slopes. RESULTS: Analysis reveals that 40-yd sprints performed on hill slopes of approximately 5.8 degrees were optimal compared with flatland running and the other slopes assessed (P < .05). Sprinting on a 5.8 degrees slope increased the subjects' maximal speed by an average of 0.35 s, resulting in a 6.5% +/- 4.0% decrease in 40-yd sprint time compared with flatland running. Compared with the 4.7 degrees slope, the 5.8 degrees slope yielded a 0.10-s faster 40-yd sprint time, resulting in a 1.9% increase in speed. CONCLUSIONS: Those who train athletes for speed should use or develop overspeed hills with slopes of approximately 5.8 degrees to maximize acute sprinting speed. The results of this study bring into question previous recommendations to use hills of 3 degrees downhill slope for this form of overspeed training.





Effect of Elastic-Cord Towing on the Kinematics of the Acceleration Phase of Sprinting

We studied the specificity of elastic-cord towing by measuring selected kinematics of the acceleration phase of sprinting. Nine collegiate sprinters ran two 20-m maximal sprints (MSs) and towed sprints (TSs) that were recorded on high-speed video (180 Hz). Sagittal plane kinematics of a 4-segment model of the right side of the body were digitized for a complete stride at the 15-m point for the fastest trial. Significant (p < 0.001) differences were observed for horizontal velocity of the center of mass (CoM), stride length (SL), and horizontal distance from the CoM of the foot to the CoM of the body. There was no significant difference in stride rate between the MS and TS conditions. Omega-squared analysis showed that elastic-cord towing accounted for most of the variance in acute changes in horizontal velocity (73%), SL (68%), and horizontal position of the CoM at foot contact (64%). Elastic-cord tow training resulted in significant acute changes in sprint kinematics in the acceleration phase of an MS that do not appear to be sprint specific. More research is needed on the specificity of TS training and long-term effects on sprinting performance.






The Effectiveness of an 8-week High Speed Treadmill Training Program on High School
Athletes.

Since the mid 1980’s, high speed treadmills have been steadily gaining popularity as a tool for increasing running
speed for speed and power sports (i.e. football, soccer, basketball, etc.). It has been used in a variety of settings with
mixed results. This study looked at integrating the technology of the high speed treadmill into an established
strength and conditioning program. A group of 29 high school athletes (28 male and 1 female) between the ages of
14 and 17 (mean=16.1) participated in an 8 week summer strength and conditioning program which consisted of
linear speed, lateral speed and agility, strength training, and the EXSpeed™ Pro treadmill program. Mean
improvements in performance were .17s in 10-yd dash, .15s in 40-yd dash, and 1.5 in. in Vertical Jump scores
respectively. The study shows that the EXSpeed™ Pro high speed treadmill training program when performed on a
treadmill with elevations up to 25% is an effective tool for speed training when properly integrated into a successful
strength and conditioning program






Leg strength and stiffness as ability factors in 100 m sprint running. (2002).

BACKGROUND: The purpose of this study was to determine the importance of leg strength and stiffness relative to i) 100 m sprint performance, ii) mean speed on the three phases of the 100 m race (30-60-100 m) and iii) the speed differences between these phases. METHODS: Nineteen regional to national level male sprinters competed in a 100 m race. Video analysis was used to determine mean velocity parameters. Two subgroups were created since some of the runners decreased their velocity during the third phase (G1), whereas others maintained or accelerated it (G2). Leg strength (concentric half-squats - counter movement jump) and stiffness (hopping) were determined. Simple (r) and multiple regressions (R) were used. RESULTS: The mean performance over 100 m was 11.43 sec (10.72-12.87 sec). The concentric half-squats were related to 100 m (r=0.74, p<0.001) and to the mean speed of each phase (R=0.75, p<0.01). The counter movement jump was related to 100 m (r=0.57, p<0.05) and was the predictor of the first phase (r=0.66, p<0.01). The hopping test was the predictor of the two last phases (R=0.66, p<0.05). Athletes who had the greatest leg stiffness (G1) produced the highest acceleration between the first and the second phases, and presented a deceleration between the second and the third ones. CONCLUSIONS: The concentric half-squats test was the best predictor in the 100 m sprint. Leg stiffness plays a major role in the second phase.






Influence of strength training on sprint running performance. Current findings and implications for training. (1997).

Today, it is generally accepted that sprint performance, like endurance performance, can improve considerably with training. Strength training, especially, plays a key role in this process. Sprint performance will be viewed multidimensionally as an initial acceleration phase (0 to 10 m), a phase of maximum running speed (36 to 100 m) and a transition phase in between. Immediately following the start action, the powerful extensions of the hip, knee and ankle joints are the main accelerators of body mass. However, the hamstrings, the m. adductor magnus and the m. gluteus maximus are considered to make the most important contribution in producing the highest levels of speed. Different training methods are proposed to improve the power output of these muscles. Some of them aim for hypertrophy and others for specific adaptations of the nervous system. This includes general (hypertrophy and neuronal activation), velocity specific (speed-strength) and movement specific (sprint associated exercises) strength training. In developing training strategies, the coach has to keep in mind that strength, power and speed are inherently related to one another, because they are all the output of the same functional systems. As heavy resistance training results in a fibre type IIb into fibre type IIa conversion, the coach has to aim for an optimal balance between sprint specific and nonspecific training components. To achieve this they must take into consideration the specific strength training demands of each individual, based on performance capacity in each specific phase of the sprint.






The effects of sprint running training on sloping surfaces.

The aim of this study was to examine the effects of sprint running training on sloping surfaces (3 degrees ) on selected kinematic and physiological variables. Thirty-five sport and physical education students were randomized into 4 training groups (uphill-downhill, downhill, uphill, and horizontal) and a control group, with 7 participants in each group. Pre- and posttraining tests were performed to examine the effects of 6 weeks of training on the maximum running speed at 35 m, step rate, step length, step time, contact time, eccentric and concentric phase of contact time, flight time, selected posture characteristics of the step cycle, and peak anaerobic power performance. Maximum running speed and step rate were increased significantly (p < 0.05) in a 35-m running test after training by 0.29 m.s(-1) (3.5%) and 0.14 Hz (3.4%) for the combined uphill-downhill group and by 0.09 m.s(-1) (1.1%) and 0.03 Hz (2.4%) for the downhill group, whereas flight time shortened only for the combined uphill-downhill training group by 6 milliseconds (4.3%). There were no significant changes in the horizontal and control groups. Overall, the posture characteristics and the peak anaerobic power performance did not change with training. It can be suggested that the novel combined uphill-downhill training method is significantly more effective in improving the maximum running velocity at 35 m and the associated horizontal kinematic characteristics of sprint running than the other training methods are.






Relationship between strength qualities and sprinting performance.

he purpose of this study was to investigate the relationship between strength measures and sprinting performance, and to determine if these relationships varied for different phases of sprint running. Twenty (11 males and 9 females) elite junior track and field athletes served as subjects. Athletes performed maximum sprints to 50 m from a block start and time to 2.5, 5, 10, 20, 30, 40 and 50 m were recorded by electronic timing gates. The resultant forces applied to the blocks were obtained from two force platforms. Twenty-seven measures of strength and speed-strength (absolute and relative to bodyweight) were collected from the height jumped and the force-time curve recorded from the takeoff phase of vertical jumping movements utilizing pure concentric, stretch shortening cycle (SSC) and isometric muscular contractions. Pearson correlation analysis revealed that the single best predictor of starting performance (2.5 m time) was the peak force (relative to bodyweight) generated during a jump from a 120 degree knee angle (concentric contraction) (r = 0.86, p = 0.0001). The single best correlate of maximum sprinting speed was the force applied at 100 ms (relative to bodyweight) from the start of a loaded jumping action (concentric contraction) (r = 0.80, p = 0.0001). SSC measures and maximum absolute strength were more related to maximum sprinting speed than starting ability. It was concluded that strength qualities were related to sprinting performance and these relationships differed for starting and maximum speed sprinting.






Sprint performance is related to muscle fascicle length in male 100-m sprinters.

The purpose of this study was to investigate the relationship between muscle fascicle length and sprint running performance in 37 male 100-m sprinters. The sample was divided into two performance groups by the personal-best 100-m time: 10.00-10.90 s (S10; n = 22) and 11.00-11.70 s (S11; n = 15). Muscle thickness and fascicle pennation angle of the vastus lateralis and gastrocnemius medialis and lateralis muscles were measured by B-mode ultrasonography, and fascicle length was estimated. Standing height, body weight, and leg length were similar between groups. Muscle thickness was similar between groups for vastus lateralis and gastrocnemius medialis, but S10 had a significantly greater gastrocnemius lateralis muscle thickness. S10 also had a greater muscle thickness in the upper portion of the thigh, which, given similar limb lengths, demonstrates an altered "muscle shape." Pennation angle was always less in S10 than in S11. In all muscles, S10 had significantly greater fascicle length than did S11, which significantly correlated with 100-m best performance (r values from -0.40 to -0.57). It is concluded that longer fascicle length is associated with greater sprinting performance.