Prior Upper Body Exercise Impairs 4-km Cycling Time-Trial Performance Without Altering Neuromuscular Function.

Purpose : This study investigated the effects of previous exhaustive upper body exercise on performance and neuromuscular fatigue following a 4-km cycling time-trial (4-km TT). Methods : Eight recreational cyclists performed a 4-km TT with (ARM _PRE ) or without (CONTR) a previous arm-crank maximal incremental test. In each experimental session, neuromuscular fatigue was evaluated with a series of electrically evoked and maximal voluntary isometric contractions (MVC). Oxygen uptake ( V ˙ O ₂ ), heart rate, electromyographic muscle activity (EMG _RMS ) and rating of perceived exertion (RPE) were also recorded throughout the 4-km TT. Results : The average power output during the 4-km TT was reduced ( P = .027) for the ARM _PRE (299 ± 59 W) group, compared with CONTR (310 ± 59 W) and overall performance in 4-km TT was impaired ( P = .021) in ARM _PRE (382 ± 28 s) compared with CONTR (376 ± 27 s). The decrease observed in MVC ( P = .033) and potentiated peak twitch force ( P = .004) at post-TT were similar between the ARM _PRE and CONTR conditions ( P = .739 and P = .493, respectively). There was no ( P = .619) change in voluntary activation at post-TT between conditions. V ˙ O ₂ , EMG _RMS and RPE measured throughout the 4-km TT were not significantly different between the conditions ( P = .558, P = .558 and P = .940, respectively). The rate of RPE change relative to power output average and heart rate was higher ( P = .030 and P = .013, respectively) in ARM _PRE (0.031 ± 0.018 AU/W and 168 ± 8 bpm) than CONTR (0.022 ± 0.010 AU/W and 161 ± 7 bpm). Conclusion : These results suggest that impaired performance in ARM _PRE was mostly due to pronounced perception of effort rather than neuromuscular fatigue.