Relationship between recovery of neuromuscular function and subsequent capacity to work above critical power.

Purpose: To investigate the relationship between the recovery of neuromuscular fatigue and the recovery of amount of work done above critical power (W´).

Methods: Ten healthy men performed, on different days, constant work rate exercises until task failure to determine critical power (CP) and W´. In the three following visits, participants performed two exhausting constant work rate exercises estimated to induce task failure within 6 min (P6 and P6), interspaced by 3, 6 or 15 min of recovery. Neuromuscular function was assessed before and periodically after the P6 using percutaneous electrical femoral nerve stimulation. The W´ recovery was measured from the total work performed above CP during the P6.

Results: The P6 induced a full use of W´ and a reduction in maximal voluntary contraction (MVC, - 19 ± 4%), voluntary activation (VA, - 6 ± 2%) and twitch force stimulated at 1 Hz (- 37 ± 11%), 10 Hz (- 50 ± 16%) and 100 Hz (- 32 ± 11%), when compared to baseline (P < 0.05). The time constant of VA recovery was significantly faster than the time constant of W´ recovery (P < 0.05), but there was no significant difference between the time constant of W´ recovery and the time constant of recovery of MVC or twitch force stimulated at 1, 10 and 100 Hz (P > 0.05). However, the time constant of W´ recovery was only associated to the time constant of MVC recovery (r = 0.73, P < 0.05).

Conclusion: The W´ recovery is not associated to the recovery of peripheral or central fatigue alone. Rather, W´ seems to be associated to the recovery of the overall capacity to generate force.