EFFECTS OF ECCENTRIC EXERCISE OF THE EXTENSORS ON ECCENTRIC EXERCISE-INDUCED MUSCLE DAMAGE OF THE FLEXORS

The magnitude of eccentric exercise-induced muscle damage is attenuated after the second bout performed by the same muscle or by the homologous muscle of the contralateral limb. This is referred to as the ipsilateral repeated bout effect and contralateral repeated bout effect, respectively. It has been shown that no muscle damage protective effect was transferred from leg to arm muscle; however, it is not known if any protective effect is conferred by antagonist muscle of the same or opposite arm or leg. PURPOSE: We tested the hypothesis that muscle damage protection effect would be induced by its antagonist muscle eccentric exercise. METHODS: Sedentary young (20-28y) men were randomly placed to six groups; three groups each for arm or leg exercise group (n = 12/group). One group performed two bouts of 30 maximal eccentric contractions (30MaxEC) of the elbow flexors (EF) or 60MaxEC of the knee flexors (KF) using a different arm (contra-EF-EF) or leg (contra-KF-KF) between bouts. The other two groups performed 30MaxEC of the elbow extensors (EE) or 60MaxEC of the knee extensors (KE) first followed by the 30MaxEC of EF or 60MaxEC of KF using the ipsilateral (ipsi-EE-EF, ipsi-KE-KF) or contralateral limb (contra-EE-EF, contra-KE-KF). The two exercise bouts were separated by 2 weeks for all groups. Changes in muscle damage markers before to 5 days following exercise were compared among the groups by mixed-design two-way ANOVAs. RESULTS: Changes in the markers following the second bout of the ipsi-EE-EF, contra-EE-EF, ipsi-KE-KF, and contra-KE-KF groups were smaller (P < 0.05) than those after the first bout of the contra-EF-EF and contra-KF-KF groups, respectively. The changes after the second bout were smaller (P < 0.05) for the ipsi-EE-EF than contra-EE-EF, and ipsi-KE-KF than contra-KE-KF group; however, those in the contra-EE-EF and contra-KE-KF groups were larger (P < 0.05) than those following the second bout of the contra-EF-EF and contra-KF-KF groups. CONCLUSION: These results showed that the magnitude of muscle damage of EF or KF was reduced by the initial bout of the extensor muscles performed by both ipsilateral and contralateral limbs, suggesting that muscle damage protective effect is conferred by the antagonist muscle in the same and opposite limb. Supported by: Funded by the National Science and Technology Council in Taiwan.