Potent protective effect conferred by four bouts of low-intensity eccentric exercise

Purpose: It is known that submaximal eccentric exercise does not confer as strong a protective effect as maximal eccentric exercise. This study tested the hypothesis that four bouts of submaximal eccentric exercise would confer a similar protective effect to one bout maximal eccentric exercise. Methods: Thirty untrained men were placed into 4 × 40% (40%) or control (CON) groups (n = 15 per group) by matching preexercise maximal voluntary isometric contraction strength (MVC). The 40% group performed 30 eccentric contractions with a load of 40% MVC (40% ECC) every 2 wk for four times followed 2 wk later by 30 maximal eccentric exercise (100% ECC) of the elbow flexors of the nondominant arm. The CON group performed two bouts of the 100% ECC separated by 2 wk. MVC at six angles, optimum angle (OA), concentric isokinetic strength (30°•s^-1 and 300°•s^-1), range of motion, upper arm circumference, plasma creatine kinase activity and myoglobin concentration, muscle soreness, and echo intensity of B-mode ultrasound images were taken before to 5 d after each exercise. Results: No significant differences in the changes in any measures were evident between the 100% ECC of the 40% group and the second 100% ECC of the CON group. Changes in all measures except for OA and upper arm circumference after the second to the fourth 40% ECC bouts were significantly smaller than those after the first 40% ECC bout. The changes in the measures after any of the 40% ECC bouts were significantly (P < 0.05) smaller than those after the first 100% ECC bout of the CON group. Conclusions: These results suggest that repeating submaximal eccentric exercise confers the same magnitude of protective effect as one bout of maximal eccentric exercise against the subsequent maximal eccentric exercise.