Immediate voluntary activation deficits following submaximal eccentric contractions of knee extensors are associated with alterations of the sense of movement

Abstract

The mechanisms underlying movement sense alterations following repeated eccentric contractions remain unclear. This study concomitantly investigated the effects of unilateral eccentric contractions on movement sense and on neuromuscular function at the knee before, immediately after (POST), 24 (POST24) and 48 (POST48) h after the exercise. Twelve participants performed sets of submaximal knee extensors (KE) eccentric contractions until a 20% decrease in maximal voluntary isometric contraction (MVIC) torque was reached. Threshold to detect passive movement (TTDPM) tasks were used to assess movement sense during both knee flexion (TTDPMFLEX) and extension (TTDPMEXT). KE fatigability was assessed using the interpolated twitch technique. TTDPM values expressed in seconds and the percentage of unsuccessful trials only increased at POST during TTDPMFLEX and TTDPMEXT. The 20%-MVIC decrease was associated with significant decreases in voluntary activation level (− 12.7%, p < 0.01) and potentiated doublet torque at 100 Hz (− 18.1%, p < 0.001). At POST24, despite persistent reductions of maximal voluntary and electrically evoked torques associated with increased perceived muscle soreness, TTDPM values and the percentage of unsuccessful trials returned to baseline values. Consequently, movement sense alterations were only observed in the presence of voluntary activation deficits, suggesting that some exercise-induced central alterations may affect the somatosensory function.

Knee position sense and knee flexor neuromuscular function are similarly altered after two submaximal eccentric bouts

“…MVICs were performed at the end of each set. Exercise was stopped when 20% MVIC force decrement was reached to correspond to fatigue levels achieved in studies on knee extensors (Da Silva et al 2021Silva et al , 2022. An additional set of 6 eccentric contractions was performed between the seated and prone JPM tasks described below to maintain the target force loss during the POST condition (Fig.…”

“…In this experiment, participants performed JPM tasks in seated and prone positions so that KF were either antagonistic or agonistic during the positioning movement. Based on recent papers showing associations between impaired VA and kinesthetic alterations (Da Silva et al 2021Silva et al , 2022, it was hypothesized that knee position sense alterations would only be observed in presence of VA decreases. It was also hypothesized that knee position sense alterations would be attenuated after ECC2.…”