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 three constant-load (80% peak power output), single-leg knee-extension trials to task failure in a randomized fashion. One trial was performed without preexisting quadriceps fatigue (CON), and two trials were performed with preexisting quadriceps fatigue induced either by voluntary (VOL; involving central motor drive) or electrically evoked (EVO; without central motor drive) quadriceps contractions (similar to 20% maximal voluntary contraction (MVC)). Neuromuscular fatigue was assessed via pre-post changes in MVC, voluntary activation (VA), and quadriceps potentiated twitch force (Q(tw,pot)). Cardiorespiratory responses and rating of perceived exertion were also collected throughout the sessions. The two prefatiguing protocols were matched for peripheral fatigue and stopped when Q(tw,pot) declined by similar to 35%. Results: Time to exhaustion was shorter in EVO (4.3 +/- 1.3 min) and VOL (4.7 +/- 1.5 min) compared with CON (10.8 +/- 3.6 min, P < 0.01) with no difference between EVO and VOL. Delta MVC (EVO: -47% +/- 8%, VOL: -45% +/- 8%, CON: -53% +/- 8%), Delta Q(tw,pot) (EVO: -65% +/- 7%, VOL: -59% +/- 14%, CON: -64% +/- 9%), and Delta VA (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 with 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.