Effect of Progressive Unilateral Eccentric versus Concentric Training on Muscle Damage of the Contralateral Limb

Abstract

Muscle damage of the elbow flexors (EF) induced by maximal eccentric exercise (100%EC) is significantly less following the second bout of the same exercise performed at 1-28 days after the first bout by not only the ipsilateral EF but also the contralateral EF (contralateral repeated bout effect: CL-RBE; Chen et al. MSSE 2016). However, it is not known whether the magnitude of the CL-RBE of the opposite limb would be differently conferred if one limb received progressive unilateral eccentric training (PET) compared with progressive unilateral concentric training (PCT). PURPOSE: This study tested the hypothesis that a greater CL-RBE would be conferred upon the EF by PET than by PCT. METHODS: Untrained young men were placed into PET, PCT and control (CON) groups (n=8/group). Both the PET and PCT groups performed 5 sets of 6 contractions of the EF of one arm once a week for 5 weeks, in which the load was increased from 10 to 30, 50, 80 and 100% of maximal voluntary isometric contraction (MVC), followed 1 week later by 5 sets of 6 100%EC of the opposite EF. The CON group performed 100%EC with one EF, and repeated the 100%EC with the opposite EF 1 week later. MVC, range of motion, upper arm circumference, muscle soreness (SOR) and plasma creatine kinase activity were measured before to 3 days after each PET and PCT, as well as before and for 5 days after 100%EC. Changes in these variables after 100%EC were compared between groups by a mixed-design two-way ANOVA. RESULTS: The magnitude of increases in MVC for the trained (22%) and untrained arms (10%) after PET was greater (P<0.05) than after PCT (11%, 5%). Changes in all variables after 100%EC were smaller (P<0.05) for the PET group (e.g. MVC: -9% at 4 days post) compared with 100%EC for the PCT group (-23%) and the first 100%EC of the CON group (-27%), without significant difference between the PCT and CON groups. Changes for the PET group (e.g. peak SOR: 12 mm) were smaller (P<0.05) than those after 100%EC for the PCT group (34 mm) and after the second 100%EC for the CON group (25 mm), and changes in all variables after the second 100%EC for the CON group were smaller (P<0.05) than for the PCT group. CONCLUSIONS: These results supported the hypothesis and showed that the CL-RBE conferred after PET would be greater than that conferred after PCT. Supported by MOST, TAIWAN (MOST105-2410-H-003-052-MY3).