Cortical voluntary activation adjustments induced by non‐exhausting eccentric exercise (1125.2)

Abstract

We tested the hypothesis that an eccentric exercise would exacerbate fatigue‐induced impairments in cortical voluntary activation and delay the recovery process, compared with a concentric‐matched trial. Fourteen males randomly performed two 30‐min walking exercises (velocity: 1 m.s‐1; grade: 25%; load: 12% of body weight), one downhill (DW) and one uphill (UP). Neuromuscular test sessions including tibial nerve and motor cortex stimulations during maximal isometric voluntary contractions of the plantar flexors were performed before and 3 min, 24 h, 48 h and 72 h post‐exercise. DW immediately reduced voluntary torque by 14.1% (P<0.001), while smaller strength losses occurred after UP (‐6.0%; P=0.15). Torque remained significantly depressed at least 3 days into recovery post‐DW (‐14.1%, ‐11.5% and ‐7.2% after 24 h, 48 h and 72 h, respectively; P<0.05). After exercise, cortical voluntary activation (‐15.9% vs. ‐8.5%; P<0.05) and resting twitch (‐42.6% vs. ‐30.2%; P=0.06) values were reduced below baseline with larger reductions after DW compared to UP, and were restored near baseline within 24 h. The capacity of the motor cortex to optimally drive the plantar flexors that accompanies peripheral fatigue is acutely impaired by non‐exhaustive eccentric exercise, but recovers within 24 h, and is therefore unlikely to explain the persisting reductions in voluntary strength capacity with the development of muscle soreness.Grant Funding Source: Supported by Aspetar and the French Délégation Générale pour l’Armement under contracts 07ca704