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

Abstract

To investigate the relationship between the recovery of neuromuscular fatigue and the recovery of amount of work done above critical power (W´). 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 6min (P61 and P62), interspaced by 3, 6 or 15min of recovery. Neuromuscular function was assessed before and periodically after the P61 using percutaneous electrical femoral nerve stimulation. The W´ recovery was measured from the total work performed above CP during the P62. The P61 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 1Hz (- 37 ± 11%), 10Hz (- 50 ± 16%) and 100Hz (- 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 100Hz (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). 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.