Contralateral Repeated Bout Effect of Eccentric Exercise of the Elbow Flexors

Purpose This study compared the magnitude of the repeated bout effect (RBE) for different time intervals between two bouts of eccentric exercise of the elbow flexors to better understand the contralateral RBE (CL-RBE). Methods Untrained young men (22.0 ± 1.8 yr) were allocated to either a control or one of seven CL-RBE groups (n = 13 per group). The CL-RBE groups performed exercise consisting of 30 maximal isokinetic (30°·s^-1) eccentric contractions of the elbow flexors (ECC1) with either dominant or nondominant arm followed 0.5 h, 6 h, 12 h, 24 h (1 d), 7 d (1 wk), 28 d (4 wk), or 56 d (8 wk) by the same exercise (ECC2) using the opposite arm. The control group used the nondominant arm for ECC1 and ECC2 separated by 2 wk. Results Maximal voluntary concentric contraction torque, peak torque angle, range of motion, upper arm circumference, muscle soreness, ultrasound echo intensity, and plasma creatine kinase activity and myoglobin concentration changed (P < 0.05) after ECC1, without significant difference among the groups. Changes in all variables after ECC2 were smaller (P < 0.05) than those after ECC1 for the control, 1 d, 1 wk, and 4 wk groups, indicating the RBE. However, the changes were not significantly different between ECC1 and ECC2 for the 0.5 h, 6 h, 12 h, and 8 wk groups. The difference in the changes in all variables between ECC1 and ECC2 was smaller for the 1 d (70%), 1 wk (55%), and 4 wk (36%) than the control group (91%), and the magnitude of the CL-RBE was reduced with increasing the time between bouts from 1 d to 4 wk (P < 0.05). Conclusion These results suggest that the CL-RBE lasts shorter than the ipsilateral RBE (>8 wk) and requires a day to be conferred.