This study investigated the hypothesis that eccentric exercise-induced muscle damage would be attenuated in muscles subjected to passive hyperthermia to a level where heat shock proteins (HSPs) were produced. Eleven male students performed a bout of 24maximal eccentric actions of the elbow flexors of one arm, and the opposite arm performed the same exercise 2-4 weeks later. One day prior to the exercise, the elbow flexors of one arm received microwave diathermy treatment resulting in muscle temperature elevation from 33-35℃to 40-42℃. The contralateral arm acted as an untreated control. Maximal isometric force (MIF), range of motion (ROM), upper arm circumference, muscle soreness with palpation, extension (SORE), and flexion, plasma creatine kinase and aldolase activity, and myoglobin concentration were measured one day prior to exercise, immediately pre- and post-exercise, and then daily for 4 days. The control arm repeated a second bout of the same exercise 4-6 weeks after the first. Changes in the criterion measures were compared between conditions (treatment vs control), or between bouts (first vs second for the control arm) by a repeated measures ANOVA. Significance level was set at P<0.05. The hyperthermia treatment had no short-term effects on muscle function prior to the exercise bout and force output and total work during exercise were not significantly different between treatment and control arms. All measures changed significantly following exercise, but the treatment arm showed significantly smaller decreases in MIF and ROM after exercise, and significantly smaller development of SORE compared to the control arm. However, these attenuation effects were not as strong as those observed following the second bout in the control arm. No significant differences between conditions were shown for other measures. These results demonstrate that elevation of muscle temperature one day prior to eccentric exercise was effective in reducing muscle damage to some extent. Although HSPs may play some role in the repeated bout effect, it is likely that other also contribute to this phenomenon.

DESCENTE SPORTS SCIENCE Vol.24/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE