Effects Of Varied Levels Of Rapid Body Weight Loss On Muscle Functions

To probe the effects of varied levels of rapid body weight loss on muscle functions, this study measured maximal isokinetic muscular strength,isokinetic endurance and anaerobic work capacity(AWC) after euhydration(0%bwl) , sauna-induced body weight loss by 2%(2%bwl)and by 4%(4%bwl)respectively in 12 healthy boy-students at P. E. department of Zhejiang University. During both maximal isokinetic muscular strength and isokinetic endurance test, we also observed iEMG and MF changes of biceps brachii,rectus femoris,vastus lateralis and vastus medialis. During the course of AWC test, we utilized rating of perceived exertion(RPE) to make an overall evaluation of muscle functions , and also to study probable mechanism. The findings turned out to be as follows:(1) Neither 2%bwl nor 4%bwl had decrement on elbow flexors> elbow extensors, knee flexors and knee extensors. However, after 2%bwl, maximal isokinetic muscular strength of elbow flexors significantly improved by 15% (P<0.05).All the maximal isokinetic muscular strength were consistence with their corresponding eletromyographic signal changes.(2)During isokinetic muscular endurance test, all the muscular endurance had no significant changes after 2%bwl; Muscular endurance of elbow flexors,knee flexors and knee extensors had no significant changes yet after 4%bwl, but that of the elbow extensors significantly decreased, the regularity of their corresponding EMG changes were as follows: just as other shudies reported that iEMG increased or decreased. Whereas the whole trend was still increase. Fortunately , MF had a better regularity, in the three different hydrations, MF of all the muscles decreased to a certain degree during the 40 times repitition fatiguing exercise.(3)2%bwl and 4%bwl had no decrement on AWC. All these suggested:(1)2%bwl and 4%bwl had no decrementive effect on maximal isokinetic muscular strength. The reason why the maximal isokinetic muscular strength increased is that the recruitment of CNS improved.(2) Neither 2%bwl nor 4%bwl had decrement on elbow flexors, knee flexors and knee extensors. But demonstrated a significant weakening role on elbow extensors after 4%bwl, which suggested that these changes might be related with the percentage of muscle fibers.(3) Neither 2%bwl nor 4%bwl had decrement on anaerobic endurance of lower extremity.(4)The changes of muscular strength,EMG and RPE all suggested that the probable mechanism of muscle fatigue after sauna-induced body weight loss didn't lie in the centre,but in the periphery.