Characterising Neuromuscular Fatigue Indices and Cycle Performance during a Time-to-Exhaustion Task and an Isowork Cycling Time-Trial

Neuromuscular fatigue indices change with increased duration and variability- of-load during cycling tasks. The purpose here was to characterise neuromuscu- lar and performance changes during and following a prolonged cycling time-to- exhaustion (TTE) task and an isowork cycling time-trial (TT). Eighteen young males (mean ± SD age: 24.7 ± 4.8 years) performed the TTE trial at a cycle- intensity eliciting a 3 mmol.L-1 blood lactate concentration. The total work per- formed during the TTE trial was recorded and used as the target in the subse- quent cycling TT, performed at least three days after the TTE trial. Maximal voluntary contraction (MVC), maximal Voluntary Activation Level (VAL) and peak doublet (PD) of quadriceps muscle was measured at baseline (PRE), post- exercise (POST) and 20-min post-exercise (POST20). Participants completed the TT (71.1 ± 3.2 min) faster (p = 0.003) than the TTE (80.9 ± 3.2 min). There were no differences in perceived exertion or any neuromuscular indices be- tween trials (all trial by time interactions: p ≥ 0.50), however, both protocols sig- nificantly (p ≤ 0.01) reduced MVC (POST:-11.8%; POST20:-8.6%), VALp (POST:-11.1%; POST20:-7.9%) and PD (POST:-24.2%; POST20:-19.9%). De-spite completing the isowork TT significantly faster than the TTE, there were no differences in central and peripheral neuromuscular fatigue indices, or levels of perceived exertion. Neuromuscular fatigue indices demonstrated only a par- tial recovery 20 min post-exercise.