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Electromyostimulation as part of a short strength-training program enhanced knee extensor strength and squat jump performance of basketball players

These results showed that an elcctrostimulation program of the latissimus dorsi increased the strength and swimming performances of a group of competitive swimmers.

Group 1 trained with maximally tolerable isometric contractions induced by ES (ELECTRICAL STIMULATION), three days a week for four weeks. Results showed that although both groups demonstrated increases in isometric strength of their quadriceps femoris muscles, training isometrically with ES produced a significantly greater increase (p < .01) than not training with ES.

The patients who received neuromuscular electrical stimulation had stronger quadriceps muscles and more normal gait patterns than those in the volitional exercise group.

In sports medicine, neuromuscular electrical stimulation (NMES) has been used for muscle strengthening, maintenance of muscle mass and strength during prolonged periods of immobilisation, selective muscle retraining, and the control of oedema. A wide variety of stimulators, including the burst-modulated alternating current ('Russian stimulator'), twin-spiked monophasic pulsed current and biphasic pulsed current stimulators, have been used to produce these effects. Several investigators have reported increased isometric muscle strength in both NMES-stimulated and exercise-trained healthy, young adults when compared to unexercised controls, and also no significant differences between the NMES and voluntary exercise groups. It appears that when NMES and voluntary exercise are combined there is no significant difference in muscle strength after training when compared to either NMES or voluntary exercise alone. There is also evidence that NMES can improve functional performance in a variety of strength tasks. Two mechanisms have been suggested to explain the training effects seen with NMES. The first mechanism proposes that augmentation of muscle strength with NMES occurs in a similar manner to augmentation of muscle strength with voluntary exercise. This mechanism would require NMES strengthening protocols to follow standard strengthening protocols which call for a low number of repetitions with high external loads and a high intensity of muscle contraction. The second mechanism proposes that the muscle strengthening seen following NMES training results from a reversal of voluntary recruitment order with a selective augmentation of type II muscle fibres. Because type II fibres have a higher specific force than type I fibres, selective augmentation of type II muscle fibres will increase the overall strength of the muscle. The use of neuromuscular electrical stimulation to prevent muscle atrophy associated with prolonged knee immobilisation following ligament reconstruction surgery or injury has been extensively studied. NMES has been shown to be effective in preventing the decreases in muscle strength, muscle mass and the oxidative capacity of thigh muscles following knee immobilisation. In all but one of the studies, NMES was shown to be superior in preventing the atrophic changes of knee immobilisation when compared to no exercise, isometric exercise of the quadriceps femoris muscle group, isometric co-contraction of both the hamstrings and quadriceps femoris muscle groups, and combined NMES-isometric exercise. It has also been reported that NMES applied to the thigh musculature during knee immobilisation improves the performance on functional tasks.

Such stimulation should be a valuable modality for developing isometric strength when normal voluntary motion is hampered. However, it appears to have little applicability to developing the kind of strength associated with rapid movements.

In conclusion glycolysis produced approximately 195 mmol ATP/kg dry muscle during the initial 48 contractions (76.8 s) and only approximately 15 mmol ATP/kg dry muscle during the final 16 contractions. Equivalent values for total ATP turnover were 278 and 16.5 mmol/kg dry muscle.

We concluded that the voluntary torque losses observed after detraining could be attributed to both neural and muscular alterations. Muscle size preservation could explain the higher knee extensor MVC values observed after the cessation of training compared to those obtained before training, therefore indicating that muscle size changes are slower than neural drive reduction.

Conclusion: EMS combined with plyometric training has proven useful for the improvement of vertical jump ability in volleyball players. This combined training modality produced rapid increases (~2 wk) of the knee extensors and plantar flexors maximal strength. These adaptations were then followed by an improvement in general and specific jumping ability, likely to affect performance on the court. In conclusion, when EMS resistance training is proposed for vertical jump development, specific work out (e.g., plyometric) must complement EMS sessions to obtain beneficial effects.

These data suggest that DJ performed before 1RM testing
may enhance squat performance in trained male athletes.

The response to a heavy resistance exercise stimulus designed to elicit postactivation potentiation appears to depend on training status. Recreationally trained individuals may exhibit fatigue in the 5 minutes following an acute heavy resistance exercise stimulus. In athletically trained individuals, however, this stimulus enhances power performance for 5 to 18.5 minutes.

It was concluded that contrast training is advantageous for increasing power output but only for athletes with relatively high strength levels.

Therefore, we examined the individual responses to the exercises and determined that 5 of the subjects did increase their vertical jumps after both squat exercises. It may be that the influence of prejump exercise on jump performance may be individualized. Nevertheless, the use of a strength ratio does not appear to predict who will benefit from posttetanic potentiation in this type of exercise situation.

The findings suggest that muscle performance during a countermovement jump can be markedly enhanced following bouts of heavy resistance training provided that adequate recovery (?8 min) is allowed between the heavy resistance training and the explosive activity.

However, an increase in force parameter during LCMJ was appeared in 80%1RM preload but not in 40%1RM. Moreover, an increase in power parameter with 80%1RM preload was remained longer than that of 40% 1RM. These results suggest that the effects of postactivation potentiation on muscular strength and power and its time course of recovery may be different from the intensity of preload.

The results showed a mean improvement of 0.098s (p<0.0001) when the second sprint was preceded by the back squats. This amounted to a 3.3% improvement on the precondition time. During the control condition, no improvement was observed between the first and second sprint. The improved sprint times observed during the E condition probably were due to a temporary increase in the efficiency of neuromuscular activation following the performance of heavy-load back squats.

The data from this study suggest that an acute bout of low-volume heavy lifting with the lower body may improve 40-m sprint times, but that loaded countermovement jumps appear to have no significant effect.

Training-induced improvements in SJ height, 80% 1 RM squat load, and maximum isometric LE force were observed (12%, 10%, and 7.7%, P<0.05). In conclusion, potentiated SJ performance occurred during a typical contrast loading protocol before the training period. However, potentiated SJ performance may alter through training, and therefore, the responsiveness of the individual should be periodically monitored and training protocols updated when necessary.

Reasons for the lack of performance enhancement can be attributed to postactivation potentiation stimulated by the SIS being insufficient in magnitude or dissipating before post-testing. This may have been due to a submaximal workload of 50% during the SIS, insufficient movement pattern specificity between the squat exercise and a CMJ, or rest intervals of excess duration.

The aim of this research was to assess the effect of a single set of contrast preloading on peak vertical displacement (PD) during a loaded countermovement jump (LCMJ) training session. These results suggest that a single set of preloading exercises enhances performance during a lower-body explosive power training session; however, the effects of a single preloading set may not peak until midway through the training session.

Results: The optimal strategy to optimize performance is a tapering intervention of 2-wk duration (overall effect = 0.59 +/- 0.33, P < 0.001), where the training volume is exponentially decreased by 41-60% (overall effect = 0.72 +/- 0.36, P < 0.001), without any modification of either training intensity (overall effect = 0.33 +/- 0.14, P < 0.001) or frequency (overall effect = 0.35 +/- 0.17, P < 0.001).

Conclusion: A 2-wk taper during which training volume is exponentially reduced by 41-60% seems to be the most efficient strategy to maximize performance gains. This meta-analysis provides a framework that can be useful for athletes, coaches, and sport scientists to optimize their tapering strategy.

These data indicated that DTR may induce larger declines in muscle power output than in maximal strength, whereas TAP may result in further strength enhancement (but not muscle power), mediated, in part, by training-related differences in IGF-1 and IGFBP-3 concentrations.

Results: The taper allowed performance gains if training was higher than a minimal level. The best performance without OT preceding the taper was reached with a load reduction of 30.8 +/- 11.8% and a duration of 19.3 +/- 2.3 d. The best performance with OT preceding the taper was significantly higher than without OT (P < 0.02) and was obtained with a significantly greater load reduction and duration, 39.3 +/- 9.9% and 28.0 +/- 5.1 d respectively. The best performance with a progressive load reduction was significantly higher than with a step reduction only with OT before the taper (102.2 +/- 1.7 vs 101.8 +/- 1.5% of performance with ODT, P < 0.005)

Conclusion: Greater training volume and/or intensity before the taper would allow higher performance gains, but would demand a greater reduction of the training load over a longer period. The results also pointed out the importance of training adaptations during the taper, in addition to fatigue dissipation.

At the end of the training period, the rats were lifting over 550% of the starting weight. Gastrocnemius size and mean fiber diameter were increased in the weight-lifting animals. This model combines exercise with positive incentive and has the advantages of being relatively easy to implement and not producing any apparent physical or mental trauma in the animal.

A new class of visuomotor neuron has been recently discovered in the monkey's premotor cortex: mirror neurons. These neurons respond both when a particular action is performed by the recorded monkey and when the same action, performed by another individual, is observed.

3. When the muscle was developing close to its maximum isometric tension, up to eight times as much movement occurred in the tendon as in the muscle fibres. This is made possible by the wallaby having a long and compliant tendon.

When the fasted-EOD rats were also exercised, they gained 29% more weight, consumed 11% more feed and had carcasses that contained 29% more lean mass and 18% less fat than the fasted-EOD rats. The data suggest that exercise may be beneficial where feed restriction is episodic, allowing some capacity for catch-up growth.

Endurance training results in increased mitochondrial density, capillary supply, changes in key metabolic enzymes, and increased maximal oxygen uptake and promotes a transition from type II to type I muscle fiber. In horses, prolonged aerobic exercise training has been shown to induce a further decline in the percentage of type IIx MyHC isoform expression and an increase of type I and IIa MyHC isoform expression. Short-duration, high-intensity exercise training stimulates type IIA and hybrid (IIA/IIX) fibers. Therefore, intensive high-speed trotting facilitates muscle fiber hypertrophy and increases the oxidative capacity of type IIX fibers.

The physical demands of rapid and economical running differ from those of physical fighting such that functional trade-offs may prevent simultaneous evolution of optimal performance in both behaviours. Here we test three hypotheses of functional trade-off by measuring determinants of limb musculoskeletal function in two breeds of domestic dogs that have undergone intense artificial selection for running (Greyhound) or fighting performance (Pit Bull). We found that Greyhounds differ from Pit Bulls in having relatively less muscle mass distally in their limbs, weaker muscles in their forelimbs than their hindlimbs, and a much greater capacity for elastic storage in the in-series tendons of the extensor muscles of their ankle joints. These observations are consistent with the hypothesis that specialization for rapid or economical running can limit fighting performance and vice versa. We suggest that functional trade-offs that prevent simultaneous evolution of optimal performance in both locomotor and fighting abilities are widespread taxonomically.

The aim of this study was to examine some metabolic properties and changes that occur in skeletal muscle and blood of greyhounds after an 800-m sprint. Three prime moving fast-twitch muscles were selected: biceps femoris (BF), gastrocnemius (G), and vastus lateralis (VL). The amount of glycogen utilized during the event was 42.57, 43.86, and 42.73 mumol glucosyl units/g wet wt, respectively. Expressed as a function of race time (48.3 +/- 0.7 s, n = 3), the mean rate of glycogen breakdown was 53.48 +/- 0.5 mumol.g wet wt-1.min-1 during the sprint. This is equivalent to an ATP turnover of 160 mumol.g wet wt-1.min-1, assuming 100% anaerobic conversion to lactate. This represents a conservative estimate, since greyhound muscle is heterogeneous and comprised of a large percentage of fast-twitch oxidative fibers (Armstrong et al., Am. J. Anat. 163: 87-98, 1982). The large decrease in muscle glycogen was accompanied by a 6- to 7-fold increase in muscle lactate from 3.48 +/- 0.13 to 25.42 +/- 3.54 (BF), 2.54 +/- 1.05 to 18.96 +/- 2.60 (G), and 4.57 +/- 0.44 to 30.09 +/- 1.94 mumol.g wet wt (VL), and a fall in muscle pH from 6.88 +/- 0.03 to 6.40 +/- 0.02 (BF), 6.92 +/- 0.02 to 6.56 +/- 0.02 (G), and 6.93 +/- 0.02 to 6.47 +/- 0.01 (VL). Cytosolic phosphorylation potential in BF decreased 10-fold from 11,360 +/- 680 to 1,184 +/- 347, and redox potential decreased 5-fold, indicating a marked reduction in the cytosol at this time.(ABSTRACT TRUNCATED AT 250 WORDS)

Skeletal limb muscles of the dog could generally be differentiated into three fibre types according to myosin adenosine triphosphatase (ATPase) (pH 9.4) and succinic dehydrogenase activities. However, because this was not always possible, for comparative purposes only, division into low myosin ATPase (slow twitch) type I and high myosin ATPase (fast twitch) type II fibres was used. The percentage of these fibre types in m deltoideus, m triceps brachii caput longum, m vastus lateralis, m gluteus medius, m biceps femoris and m semitendinosus was examined in the greyhound, crossbred and foxhound. In all muscles the greyhound had a significantly higher percentage of fibres with high myosin ATPase activity at pH 9.4 than the other breeds, with almost 100 per cent in most muscles examined. The activities of nine enzymes and glycogen concentration were determined in m gluteus medius and m semitendinosus of the greyhound and crossbred. Significantly higher levels of creatine kinase, aldolase, alanine aminotransferase and citrate synthase and significantly lower activities of 3-hydroxyacyl coenzyme A dehydrogenase and hexokinase were found in both muscles of the greyhound. The implications of these findings are discussed.