We analyzed the relation between subjective fatigue by hard exercise and stress hormone and cytokine data. The subjects are eight healthy men who had exercise experience. In this experiment, hard exercise was carried out in the first place. After two-hour rest, a performance test was carried out. The blood test was conducted 4 times (before exercise, after exercise, rest, and a performance test). Subjective fatigue was indicated using visual analogue scale (VAS). After the hard exercise and performance test, VAS increased and showed the significant difference. Lactic acid, adrenaline, noradrenaline, growth hormone, IL-6, and IL-8 increased after each exercise and showed the significant difference. Subjective fatigue and the value of lactic acid, and IL-6 showed significant positive correlations. These results suggest that lactic acid, and IL-6 may become an index of fatigue in this exertion model.

This study was designed to investigate the effects of supplementing soy peptide on isometric performances and serum CK and LDH trends after a high intensity eccentric exercise stress. Study subjects consisted of 13 males and were divided into 2 groups. They were instructed to take 4,000 mg of soy peptide or placebo orally before and for 7 days following the initial exercise stress. Soy peptide group revealed significantly faster improvements in knee extension performance at 72 hr-post the eccentric exercise (p<0.05). Comparing with placebo group, soy peptide group showed significantly lower serum LDH activity 168 hr after the exercise (p<0.05), while as to serum CK levels, significant difference was not observed between those 2 groups. These results indicate that oral supplementation of soy peptide could induce not only reduction in serum LDH activity level, but also faster recovering in isometric performance after high intensity repetitive eccentric exercise.

A double-blind placebo-controlled trial was undertaken to evaluate the synergic effects of coenzymeQ10 (CoQ10) and creatine (Cr) through oral supplementation on the intermittent short duration high-intensity exercise on a cycle ergometer. Twenty-eight male athletes were divided into four groups of CoQ10 and Cr (CoQ10+Cr), CoQ10 (CoQ10+Pl), Cr (Pl+Cr) and placebo group (Pl+Pl). Each participant was instructed to have 100 mg of CoQ10 and/or 5 g of Cr per day for 2 weeks. Repetitive 5 bouts of 10-sec high-intensity cycle exercise tests were performed before and after supplementations. After supplementations, subjects in (CoQ10+Cr) revealed most improved performance in mean power outputs at the 2^nd (p<0.05), the 3^rd (p<0.05), the 4^th (p<0.05) and the 5^th set (p=0.06), comparing with the participants in the other 3 groups. These findings suggest that enhanced mean power output on repetitive short duration high-intensity exercise can be acquired after supplementing CoQ10 combined with Cr.