Activation of skeletal muscle mechanoreceptors and nociceptors reduces the exercise performance of the contralateral homologous muscles.

ABSTRACT

INTRODUCTION: Increasing evidence suggests that activation of muscle nerve afferents may inhibit central motor drive, affecting contractile performance of remote exercising muscles. While these effects are well documented for metaboreceptors, very little is known about the activation of mechano- and mechano-nociceptive afferents on performance fatigability. Therefore, the purpose of the present study was to examine the influence of mechanoreceptors and nociceptors on performance fatigability. METHODS: Eight healthy young males undertook four randomized experimental sessions on separate occasions in which the experimental knee extensors were a) resting (CTRL), b) passively stretched (ST), c) resting with DOMS (DOMS), or d) passively stretched with DOMS (DOMS+ST), while the contralateral leg performed an isometric time to task failure (TTF). Changes in maximal voluntary contraction (ΔMVC), potentiated twitch force (ΔQtw,pot) and voluntary muscle activation (ΔVA) were also assessed. RESULTS: TTF was reduced in DOMS+ST (-43%) and ST (­29%) compared with CTRL. DOMS+ST also showed a greater reduction of VA (-25% vs ­8%, respectively) and MVCcompared with CTRL (­28% vs -45%, respectively). RPE was significantly increased at the initial stages (20-40-60%) of the TTF in DOMS+ST compared with all conditions. CONCLUSION: These findings indicate that activation of mechanosensitive and mechano-nociceptive afferents of a muscle with DOMS reduces TTF of the contralateral homologous exercising limb, in part by reducing VA so accelerating mechanisms of central fatigue.