Alterations of Neuromuscular Function after the World's Most Challenging Mountain Ultra-Marathon

We investigated the physiological consequences of the most challenging mountain ultra-marathon (MUM) in the world: a 330-km trail run with 24000 m of positive and negative elevation change. Neuromuscular fatigue (NMF) was assessed before (Pre-), during (Mid-) and after (Post-) the MUM in experienced ultra-marathon runners (n = 15; finish time = 122.43 hours +/- 17.21 hours) and in Pre- and Post-in a control group with a similar level of sleep deprivation (n = 8). Blood markers of muscle inflammation and damage were analyzed at Pre- and Post-. Mean +/- SD maximal voluntary contraction force declined significantly at Mid- (-13 +/- 17% and -10 +/- 16%, P<0.05 for knee extensor, KE, and plantar flexor muscles, PF, respectively), and further decreased at Post- (-24 +/- 13% and -26 +/- 19%, P<0.01) with alteration of the central activation ratio (-24 +/- 24% and -28 +/- 34% between Pre- and Post-, P<0.05) in runners whereas these parameters did not change in the control group. Peripheral NMF markers such as 100 Hz doublet (KE: -18 +/- 18% and PF: -20 +/- 15%, P<0.01) and peak twitch (KE: -33 +/- 12%, P<0.001 and PF: -19 +/- 14%, P<0.01) were also altered in runners but not in controls. Post-MUM blood concentrations of creatine kinase (3719 +/- 3045 Ul.(1)), lactate dehydrogenase (1145 +/- 511 UI.L-1), C-Reactive Protein (13.1 +/- 7.5 mg.L-1) and myoglobin (449.3 +/- 338.2 mu g.L-1) were higher (P<0.001) than at Pre- in runners but not in controls. Our findings revealed less neuromuscular fatigue, muscle damage and inflammation than in shorter MUMs. In conclusion, paradoxically, such extreme exercise seems to induce a relative muscle preservation process due likely to a protective anticipatory pacing strategy during the first half of MUM and sleep deprivation in the second half.