Introduction: Eccentric exercise elicits considerable muscle damage. If a bout of unilateral eccentric exercise is repeated on the ipsilateral or contralateral limb, a repeated bout effect (RBE) may be observed where muscle damage is attenuated. Purpose: To examine whether a RBE exists following repeated bouts of damaging eccentric exercise in the ipsilateral and contralateral limbs, and assess changes to motor unit firing characteristics in both limbs following recovery from an initial bout. Methods: Sixteen untrained men were randomized into exercise (EX) or control (CON) groups. EX performed eccentric exercise of the elbow flexors on the dominant (ipsilateral) limb and repeated the exercise protocol on both ipsilateral and contralateral limbs fourteen days later. Range of motion (ROM), proximal and distal measures of muscle soreness (pVAS/dVAS) and pain-pressure threshold (pPPT/dPPT), maximal isometric torque (MVIC), rate of torque development (RTD) at 50ms (RTD50), 100ms (RTD100), 200ms (RTD200), and peak RTD (RTDpeak) were assessed at baseline (BL), immediately-post (IP), and at twenty-four (24H) and seventy-two hours (72H) post-exercise in EX and CON. Motor unit (MU) firing characteristics were assessed in both limbs via decomposition of surface electromyography (EMG) signals collected during submaximal ramp contractions at 50% and 80% MVIC. Results: Changes in ROM and RTD200 indicated a RBE in both limbs, whereas changes in MVIC and RTD100 indicated a RBE in the ipsilateral limb only. Changes in RTD50, RTDpeak, pPPT, or dPPT did not support a RBE. Increases in the slopes of both the mean firing rate vs. recruitment threshold and the action potential amplitude vs. recruitment threshold relationships at 80% MVIC were noted between bouts for the ipsilateral limb in EX, but not the contralateral limb. Conclusions: Results of this study provide support for a RBE in both limbs, whereas alterations to MU firing characteristics were noted in the ipsilateral limb only.
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Doctor of Philosophy (Ph.D.)
College of Community Innovation and Education
Learning Sciences and Educational Research
Education; Exercise Physiology
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Coker, Nicholas, "Effect of Unaccustomed Eccentric Exercise on Motor Unit Firing Characteristics and the Contralateral Repeated Bout Effect: A Pilot Study" (2020). Electronic Theses and Dissertations, 2020-. 199.