Prior Involvement of Central Motor Drive does not Impact Performance and Neuromuscular Fatigue in a Subsequent Endurance Task

Purpose: This study evaluated whether central motor drive during fatiguing exercise plays a role in determining performance and the development of neuromuscular fatigue during a subsequent endurance task. Methods: On separate days, 10 males completed 3 constant-load (80% peak-power output), single-leg knee-extension trials to task failure in a randomized fashion. One trial was performed without pre-existing quadriceps fatigue (CON), and 2 trials were performed with pre-existing, quadriceps fatigue induced either by voluntary (VOL; involving central motor drive) or electrically-evoked (EVO; without central motor drive) quadriceps contractions (~20% maximal voluntary contraction (MVC)). Neuromuscular fatigue was assessed via pre-post changes in MVC, voluntary activation (VA), and quadriceps potentiated twitch force (Qtw,pot). Cardiorespiratory responses and rating of perceived exertion were also collected throughout the sessions. The two pre-fatiguing protocols were matched for peripheral fatigue and stopped when Qtw,pot declined by ~35%. Results: Time-to-exhaustion was shorter in EVO (4.3 ± 1.3 min) and VOL (4.7 ± 1.5 min) compared to CON (10.8 ± 3.6 min, p < 0.01) with no difference between EVO and VOL. ΔMVC (EVO:-47 ± 8%, VOL:-45 ± 8%, CON:-53 ± 8%), ΔQtw,pot (EVO:-65 ± 7%, VOL:-59 ± 14%, CON:-64 ± 9%), ΔVA (EVO:-9 ± 7%, VOL:-8 ± 5%, CON:-7 ± 5%) at the end of the dynamic task were not different between conditions (all p > 0.05). Compared to EVO (10.6 ± 1.7) and CON (6.8 ± 0.8), rating of perceived exertion was higher (p = 0.05) at the beginning of VOL (12.2 ± 1.0). Conclusions: These results suggest that central motor drive involvement during prior exercise plays a negligible role on the subsequent endurance performance. Therefore, our findings indicate that peripheral fatigue-mediated impairments are the primary determinants of high-intensity single-leg endurance performance.