Abstract
The study aimed to investigate the effect of fatigue on static and dynamic postural stability after completing a mountain ultra-marathon. Twelve male athletes participated in the study. Postural stability was assessed before and immediately after the race. Static postural stability was evaluated on a dynamometric platform with eyes opened (OE) and closed (CE). Dynamic postural stability was assessed with OE on an instrumented plate which allowed medio-lateral oscillations. Stabilometric data were affected by fatigue in the OE condition, concerning sway path velocity (p = 0.0006), sway area velocity (p = 0.0006), area of the confidence ellipse (p = 0.0016), maximal anterior-posterior (AP) (p = 0.0017) and medio-lateral (ML) (p = 0.0039) oscillations. In the CE condition the sway path velocity (p = 0.0334), the maximal ML oscillations (p = 0.0161) and the area of the confident ellipse (p = 0.0180) were also negatively influenced. Stabilogram diffusion analysis showed in the OE condition an increase of short-term diffusion coefficients considering the anterior-posterior direction (Dfys; p = 0.0023) and the combination of the two (Dfr2s; p = 0.0032). Equally, long term diffusion coefficients increased considering the anterior-posterior direction (Dfyl; p = 0.0093) and the combination of the two (Dfr2l; p = 0.0086). In CE condition greater values were detected for medio-lateral direction (Dfxl; p = 0.033), anterior-posterior direction (Dfyl; p = 0.0459) and the combination of the two (Dfr2l; p = 0.0048). The dynamic postural stability test showed an increase of the time spent with the edges of the plate on the floor (p = 0.0152). Our results showed that mountain ultra-marathon altered static stability more than dynamic stability. An involvement of cognitive resources to monitor postural stability after fatiguing could be the explanation of the worsening in the automatic task (quiet standing) and of the positive compensation in the less automatic task (dynamic standing on the instrumented plate).
Highlights
The maintenance of postural stability depends on the complex interaction among visual, vestibular and somatosensory systems to keep the centre of gravity (CoG) within the base of support
Muscular exercise is recognised to be one of the causes of postural stability deterioration in human subjects and several factors contribute to its worsening
In the present study we focused our attention in postural stability variations after an 80 km mountain ultra-marathon by means of a combination of static and dynamic stability tests
Summary
The maintenance of postural stability depends on the complex interaction among visual, vestibular and somatosensory systems to keep the centre of gravity (CoG) within the base of support To ensure this condition in an upright posture, contractions of several postural muscles controlled by the central nervous system are needed [1]. From a biomechanical point of view the measurement of the centre of pressure (CoP) displacement by means of force platforms is the most employed system to evaluate static upright posture. This methodology of postural assessment proved good intra-session and inter-session reliability, above all referred to sway length, CoP X and CoP Y parameters [2]. Post exercise balance impairment is usually associated to prolonged exercise and recent findings showed how in short intensive exercises the increase of postural sway is due to the hyperventilation more than to muscle fatigue [11]
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