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Neuromuscular Consequences of an Extreme Mountain Ultra-Marathon
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Edité par CCSD ; Public Library of Science -
International audience. We investigated the physiological consequences of one of the most extreme exercises realized by humans in race conditions: a 166-km mountain ultra-marathon (MUM) with 9500 m of positive and negative elevation change. For this purpose, (i) the fatigue induced by the MUM and (ii) the recovery processes over two weeks were assessed. Evaluation of neuromuscular function (NMF) and blood markers of muscle damage and inflammation were performed before and immediately following (n = 22), and 2, 5, 9 and 16 days after the MUM (n = 11) in experienced ultra-marathon runners. Large maximal voluntary contraction decreases occurred after MUM (235% [95% CI: 228 to 242%] and 239% [95% CI: 232 to 246%] for KE and PF, respectively), with alteration of maximal voluntary activation, mainly for KE (219% [95% CI: 27 to 232%]). Significant modifications in markers of muscle damage and inflammation were observed after the MUM as suggested by the large changes in creatine kinase (from 144694 to 13,633612,626 UI L 21), myoglobin (from 32622 to 1,43261,209 mg L 21), and C-Reactive Protein (from ,2.0 to 37.7626.5 mg L 21). Moderate to large reductions in maximal compound muscle action potential amplitude, high-frequency doublet force, and low frequency fatigue (index of excitation-contraction coupling alteration) were also observed for both muscle groups. Sixteen days after MUM, NMF had returned to initial values, with most of the recovery process occurring within 9 days of the race. These findings suggest that the large alterations in NMF after an ultra-marathon race are multi-factorial, including failure of excitation-contraction coupling, which has never been described after prolonged running. It is also concluded that as early as two weeks after such an extreme running exercise, maximal force capacities have returned to baseline.
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