Fatigue and Recovery after Single-Stage versus Multistage Ultramarathon Running

Ultramarathon running includes two main types of events: single-stage race (SSR) and multistage races (MSR). Direct comparison of neuromuscular fatigue and recovery after SSR versus MSR race of comparable distance and elevation has never been performed. The aim of this study was to assess neuromuscular fatigue and recovery after two ultramarathons of equal distance performed either (i) in a single stage or (ii) in four successive days.

Thirty-one runners participated in the study: 17 ran 169 km in a single-stage race and 14 performed around 40 km·d over 4 d. The two races were performed on the same course. Neuromuscular function was tested before (PRE), after (POST), and 2 (D + 2), 5 (D + 5) and 10 (D + 10) days after the races. Neuromuscular function was evaluated on both knee extensors (KE) and plantar flexors (PF) with voluntary and evoked contractions using electrical (femoral and tibial, respectively) nerve stimulation.

Reduction of voluntary activation measured in the KE was greater (i.e., central fatigue) for SSR than MSR directly after the race (-23% vs -7%), P < 0.01). Reductions in evoked mechanical KE and PF responses on relaxed muscle (i.e., peripheral fatigue) of both KE and PF took longer to recover in MSR than in SSR.

Performing prolonged running exercise over several days, each separated by rest, elicits more prolonged impairments in contractile function compared with single-stage ultramarathon, whereas single-stage mountain ultramarathon ran on the same course is associated with greater central fatigue.