Neuromuscular Consequences of an Extreme Mountain Ultra-Marathon

Abstract

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 (−35% [95% CI: −28 to −42%] and −39% [95% CI: −32 to −46%] for KE and PF, respectively), with alteration of maximal voluntary activation, mainly for KE (−19% [95% CI: −7 to −32%]). Significant modifications in markers of muscle damage and inflammation were observed after the MUM as suggested by the large changes in creatine kinase (from 144±94 to 13,633±12,626 UI L−1), myoglobin (from 32±22 to 1,432±1,209 µg L−1), and C-Reactive Protein (from <2.0 to 37.7±26.5 mg L−1). 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.

Low markers of muscle damage and inflammation following a 3-day trail run

“…Further evidence is the fact that TC was not significantly elevated at any post-stage or post-race time-point, but was reduced after S1 (p<0.001), confirming previous findings of reduced swelling and a post-race decrease in muscle mass. 16 The low systemic markers of muscle damage and inflammation, when compared with previous findings following the Comrades Marathon 16 confirm the findings of Millet et al 1 who, in their study on the neuromuscular consequences of extreme running in a 166 km mountain ultra-marathon, reported that post-race serum concentrations of CPK, hsCRP and neutrophils were lower than those measured after a road race with similar finishing times. 1 These researchers attributed their findings of low concentrations of systemic markers of muscle damage and inflammation to the relatively soft underfoot surfaces and to the athletes frequently being forced to walk, jump and climb due to the technical demands of the terrain.…”

“…1 The sporadic increases in intensity of effort, rises in T intest , substantial body mass loss and increases in serum osmolality during the event, did not confirm previous suggestions 3,4,11 that thermal and hydration status is directly related to the degree of muscle damage. It would be of interest to the investigate the impact of pre-race preparation on markers of muscle damage and inflammatory response found following this multi-day trail running event and to control the nutritional and fluid intake in future field work on multiday trail running.…”

“…1 These are generally regarded as more strenuous than road running due to the nature of the trails, which can involve diverse challenges including single track paths on steep ascends and descends in mountains, crossing rivers and running along grasslands and through forests. 2 Although physiological response to single-day trail running has been assessed, [1][2][3][4] the cumulative effects of multi-day trail running on markers of muscle damage and inflammation have not yet been reported. Prolonged endurance exercise causes muscle damage that initiates an inflammatory response and subsequent remodelling of muscle.…”

Electrical stimulation for testing neuromuscular function: from sport to pathology

“…Other examples can be found in (1) training adaptations which can be evidenced by ES often combined with voluntary contractions and EMG measurements (Van Cutsem et al 1998) or (2) fatigue in athletes. Another example is the fact that extreme running (over 24 h) induces large central fatigue and changes at the muscle level that are highly variable and dependent on the course proWle and muscle group (Martin et al 2010;Millet et al 2011).…”

High-intensity sprint fatigue does not alter constant-submaximal velocity running mechanics and spring-mass behavior

“…These changes may contribute to attenuate the potentially harmful eccentric phase and overall load faced by their musculo-skeletal system at each step (Morin et al 2011a, b), which may not be an issue of importance during exhaustive runs of shorter durations. Further support to this hypothesis was given by the absence of correlation observed between the changes in running pattern and the large losses of force (maximal voluntary contraction, MVC) observed in the knee extensors and plantar flexors (Martin et al 2010;Millet et al 2011). Furthermore, the changes in running pattern reported after ULD were very consistent (a) with an overall decrease in the amplitude of oscillation of the spring-mass system at each step, and (b) with changes reported in particular situations where an impairment of muscular function and/or structure and/or localized pain was induced by a muscular biopsy of the vastus lateralis (Morin et al 2009a) or by the natural ageing process (Cavagna et al 2007;Karamanidis and Arampatzis 2005).…”