Abstract
It is well knows that postural control (PC) is deteriorated with neuromuscular fatigue, altitude or sleep deprivation induced by a mountain ultra-marathon (MUM). Several regulatory mechanisms have also been reported during this type of event and the changes in PC at different points of MUM remain unknown. The purpose of this study was to investigate the time course of PC during an extreme MUM. We tested the hypothesis that PC alteration would not increase linearly.Methods: 16 participants (age 45.1 ± 9.6 years) were tested bipedaly on a posturographic platform for 51.2 s with eyes open every ∼50 km. Both traditional and stabilogram diffusion analyses (SDA) were performed. A visual analog scale (VAS) was used for a subjective evaluation of global fatigue, sleep feeling and pain.Results: The main parameters (center of pressure trajectory analysis) increased significantly (p < 0.001, d = 1.56, very large) until km 100. This was confirmed by SDA in the antero-posterior plane. Short term effective diffusion coefficient significantly increased (p < 0.001, d = 1.07, very large) as critical point (p < 0.01, d = 1.57, very large). From km 100 to 200, a different response was observed with a continuous decrease in most of the PC parameters. This was confirmed by SDA in the antero-posterior plane. Short term effective diffusion coefficient significantly increased (p < 0.001, d = 1.39, very large) as critical point (p < 0.01, d = 1.51, very large).Conclusion: Posture alteration is progressively increased until 100 km. After this point, compensatory mechanisms appear to limit the posture degradation. This bi-phasic response is of interest for better understanding the coping with extreme fatigue.
Highlights
Mountain Ultra-Marathon (MUM) races have become more and more popular in recent years (Millet et al, 2011; Millet and Millet, 2012; Saugy et al, 2013; Vernillo et al, 2015a; Degache et al, 2016; Zakovska et al, 2017)
Postural stability can be affected by sleep deprivation, but this last study showed minimal alterations in balance in controls with the same level of sleep deprivation, that’s why their conclusion was that the postural alterations originated predominantly from the MUM characteristics, and from muscle fatigue, and not from sleep deprivation itself (Degache et al, 2014)
∗p < 0.05, ∗∗p < 0.01, ∗∗∗p < 0.001 for differences compared to PRE, $$p < 0.01, $$$p < 0.001 for differences compared to 50 km, #p < 0.05, #p < 0.05, ##p < 0.01, ###p < 0.001 for differences compared to 106 km
Summary
Mountain Ultra-Marathon (MUM) races have become more and more popular in recent years (Millet et al, 2011; Millet and Millet, 2012; Saugy et al, 2013; Vernillo et al, 2015a; Degache et al, 2016; Zakovska et al, 2017) These events involve a distance longer than traditional marathons on mountain trails (Millet and Millet, 2012). Studies of this type of extreme race are Postural Control During Ultra-Endurance Race an opportunity to investigate the physiological impact on the human body (Millet and Millet, 2012; Zakovska et al, 2017; Knechtle and Nikolaidis, 2018). Postural stability can be affected by sleep deprivation, but this last study showed minimal alterations in balance in controls with the same level of sleep deprivation, that’s why their conclusion was that the postural alterations originated predominantly from the MUM characteristics, (e.g., altitude, running uphill/downhill) and from muscle fatigue, and not from sleep deprivation itself (Degache et al, 2014)
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