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This study investigated the effects of moderate dehydration (~2.5% body weight) on muscle strength and endurance using percutaneous electrical stimulation to quantify central and peripheral fatigue, and isolate the combined effects of exercise-heat stress and dehydration, vs. the effect of dehydration alone. Force production and voluntary activation were calculated in 10 males during 1 brief and 15 repeated maximal voluntary isometric contractions performed prior to (control) walking in the heat (35°C), immediately following exercise, and the next morning (dehydration). The protocol was also performed in a euhydrated state. During the brief contractions, force production and voluntary activation were maintained in all trials. In contrast, force production decreased throughout the repeated contractions, regardless of hydration status (P<0.001). The decline in force was greater immediately following exercise-heat stress dehydration compared with control and euhydration (P<0.001). When dehydration was isolated from acute post-exercise dehydration, force production was maintained similarly to control and euhydration. Despite the progressive decline in force production and the increased fatigability observed during the repeated contractions, voluntary activation remained elevated throughout each muscle function test. Therefore, moderate dehydration, isolated from acute exercise-heat stress, does not appear to influence strength during a single contraction or enhance fatigability.

The knowledge gained through this study could help to make plyometric training more effective when Proprioceptive Neuromuscular Facilitation (PNF) stretching added to the workouts without having to isolate strength and flexibility on separate sessions. The aim of this study was to compare the individual and combined effects of 6-week of PNF stretching and plyometric training (PLYOT) in muscular power and flexibility for young volleyball players Thirty-seven male young volleyball players participated in the current study. They were distributed into four groups; PNF (n = 10), PLYOT (n = 10), Combining PNF and PLYOT (COMB) (n = 10), and control group without PNF and PLYOT (CON) (n = 7), they were tested before (PRE) and after (POST) 6-week training for muscular power [i.e. vertical jump (VJ), seated medicine ball throw (SMTH), and rotational power ball throw (RPTH)] and flexibility [i.e. sit& reach test (SRT), shoulder& wrist flexibility test (SWFT), and trunk rotation test (TRT)]. The results have shown significant effects of the time for all study variables (p ≤ 0.05) of all groups except CON group had no significant effects (p ˃ 0.05). There were statistically significant differences favor COMB group (p ≤ 0.05) at the POST evaluation in muscular power variables in comparison with the PNF and PLYOT groups, while no statistically significant differences (p ˃ 0.05) were found between PNF, PLYOT, and COMB in all flexibility variables. In conclusion the combined effect of PNF and PLYOT has surpassed the individual effect of them on muscular power but not on flexibility variables.

Creatine phosphokinase (CPK) is a binary enzyme that stimulates reverse phosphorylation to regenerate adenosine triphosphate. Creatine supplementation improves the Phosphagen system by increasing the amount of free creatine and phosphocreatine available to replenish adenosine triphosphate. The aims of this study are to investigate the effects of a creatine supplement on CPK enzyme, muscular endurance, power and agility performance compared to a placebo among wrestlers during the competition in a double-blind and randomized manner. Sixteen Wrestlers participated in the current study. They were divided into two groups; Experimental group (EXP) (n = 8) with creatine supplementation and a control group without creatine supplementation (CON) (n = 8). They were tested before (PRE) and after (POST) 8-week creatine supplementation period for CPK enzyme, muscular endurance [i.e. back-throw skill using the wrestling dummy], power [i.e. skill of the bridge], and agility [i.e. skill of the bridge in 10 sec.]. The results have shown statistically significant effects of the time (i.e. pre- to post-training) for all measured variables (p ≤ 0.05) of EXP group (whereas no significant effects (p ˃ 0.05) of CON group. There were statistically significant differences (p ≤ 0.05) at the POST evaluation of EXP group in comparison with CON group for all study variables.