The repeated-bout effect: influence on biceps brachii oxygenation and myoelectrical activity

Abstract

This study investigated biceps brachii oxygenation and myoelectrical activity during and following maximal eccentric exercise to better understand the repeated-bout effect. Ten men performed two bouts of eccentric exercise (ECC1, ECC2), consisting of 10 sets of 6 maximal lengthening contractions of the elbow flexors separated by 4 wk. Tissue oxygenation index minimum amplitude (TOI(min)), mean and maximum total hemoglobin volume by near-infrared spectroscopy, torque, and surface electromyography root mean square (EMG(RMS)) during exercise were compared between ECC1 and ECC2. Changes in maximal voluntary isometric contraction (MVC) torque, range of motion, plasma creatine kinase activity, muscle soreness, TOI(min), and EMG(RMS) during sustained (10-s) and 30-repeated isometric contraction tasks at 30% (same absolute force) and 100% MVC (same relative force) for 4 days postexercise were compared between ECC1 and ECC2. No significant differences between ECC1 and ECC2 were evident for changes in torque, TOI(min), mean total hemoglobin volume, maximum total hemoglobin volume, and EMG(RMS) during exercise. Smaller (P < 0.05) changes and faster recovery of muscle damage markers were evident following ECC2 than ECC1. During 30% MVC tasks, TOI(min) did not change, but EMG(RMS) increased 1-4 days following ECC1 and ECC2. During 100% MVC tasks, EMG(RMS) did not change, but torque and TOI(min) decreased 1-4 days following ECC1 and ECC2. TOI(min) during 100% MVC tasks and EMG(RMS) during 30% MVC tasks recovered faster (P < 0.05) following ECC2 than ECC1. We conclude that the repeated-bout effect cannot be explained by altered muscle activation or metabolic/hemodynamic changes, and the faster recovery in muscle oxygenation and activation was mainly due to faster recovery of force.

Lengthening our perspective: Morphological, cellular, and molecular responses to eccentric exercise

“…Figure illustrates the typical reductions in strength loss, soreness, and CK found following a repeated exercise bout, though there is a high degree of variability for the reduction based on the study design (exercise mode/intensity/muscle group) and among individuals. Many recent papers have attempted to dissect the parameters of an original stimulus needed to evoke a significant protective effect . Only a few studies to date have focused on cellular and molecular manifestations of damage with repeated exercise bouts.…”

Attenuation of Eccentric Exercise–Induced Muscle Damage by Preconditioning Exercises

“…Several studies have been published since the McHugh review paper (16) and have provided evidence for or against the potential adaptations. For example, Muthalib et al (17) compared the first and second maximal eccentric exercise bouts of the elbow flexors using surface EMG and near-inirared spectroscopy and showed that the protective effect could not be explained by altered muscle activation or metabolic/ hemodynamic changes. Mackey et al (14) have recently reported that extracellular matrix is strengthened after 180 isometric contractions evoked by electrical stimulation, and muscle damage in the subsequent bout performed 28 d later was aftenuated.…”

Eccentric contraction–induced muscle damage in human flexor pollicis brevis is accompanied by impairment of motor nerve

“…Previous investigations of ECC‐induced muscle damage have focused on the elbow flexors and knee extensors . Symptoms of muscle damage include a decline in MVC, DOMS, limited range of motion (ROM), swelling in skeletal muscle, and increased serum creatine kinase (CK) levels after exercise .…”