Neuromuscular fatigability is not affected by the contraction pattern of exercises with a similar mean torque.

Abstract

Purpose: Neuromuscular fatigability is task-dependent, but the influence of the contraction pattern on neuromuscular fatigability is largely unknown. Therefore, the present study aims to investigate if neuromuscular fatigability is affected by the contraction pattern of exhausting isometric exercises.

Methods: Thirteen participants sustained a plantar flexors MVC for 1 min (MVC_1-MIN) before and after exhausting exercises designed to produce a similar mean torque (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.

Results: 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 MVC_1-MIN increased after all exercises to a similar extent, mainly because of neural alterations. Contrary to MVC, the torque loss during the MVC_1-MIN returned to baseline value after the recovery period.

Conclusion: INT, CON and VAR exercises, performed with identical mean torque and until exhaustion, led to a similar neuromuscular fatigability. When the mean torque is matched among exercises, the contraction pattern does not influence the extent of neuromuscular fatigability, assessed through the maximal torque production and sustainability. The present findings are crucial to consider for the management of neuromuscular fatigability in physical conditioning in both athletes and patients.