Mean exercise torque is a critical factor influencing neuromuscular fatigability induced by exhausting contractions

Abstract

PURPOSETo get a more detailed description of neuromuscular fatigability, maximal torque sustainability (i.e., the ability to maintain a high torque level) can be assessed in addition to the classically used maximal voluntary contraction (MVC). Since this parameter appears to be affected by mean exercise torque (MET), the present study aims to examine the relationship between MET and neuromuscular fatigability induced by exhausting contractions. METHODSThirteen participants sustained a plantar flexors MVC for 1 min (MVC1- MIN) before and after exhausting exercises designed to produce a similar MET (30% MVC), and following a 10-min rest period. Exercises consisted of intermittent (INT), continuous (CON) or variable (continuous contraction alternating between moderate and low intensity, VAR) contractions performed until task failure. RESULTSAlthough the INT resulted in greater exercise duration and torque-time integral than CON and VAR, MVC similarly decreased after all exercises due to neural and muscular impairments. The torque loss during the MVC1-MIN increased after all exercises to a similar extent, mainly because of neural alterations. Contrary to MVC, the torque loss during the MVC1-MIN returned to baseline value after the recovery period. CONCLUSIONBy considering both maximal torque production and sustainability, INT, CON and VAR exercises, performed with identical mean torque and until exhaustion, led to a similar neuromuscular fatigability. Results confirm the independence of maximal torque production from the contraction pattern and support the impact of MET on maximal torque sustainability. The present findings are crucial to consider for the management of neuromuscular fatigability in both athletes and patients.