Effect of the Fatigue Induced by a 110-km Ultramarathon on Tibial Impact Acceleration and Lower Leg Kinematics

Abstract

Ultramarathon runners are exposed to a high number of impact shocks and to severe neuromuscular fatigue. Runners may manage mechanical stress and muscle fatigue by changing their running kinematics. Our purposes were to study (i) the effects of a 110-km mountain ultramarathon (MUM) on tibial shock acceleration and lower limb kinematics, and (ii) whether kinematic changes are modulated according to the severity of neuromuscular fatigue. Twenty-three runners participated in the study. Pre- and post-MUM, neuromuscular tests were performed to assess knee extensor (KE) and plantar flexor (PF) central and peripheral fatigue, and a treadmill running bouts was completed during which step frequency, peak acceleration, median frequency and impact frequency content were measured from tibial acceleration, as well as foot-to-treadmill, tibia-to-treadmill, and ankle flexion angles at initial contact, and ankle range of motion using video analysis. Large neuromuscular fatigue, including peripheral changes and deficits in voluntary activation, was observed in KE and PF. MVC decrements of ~35% for KE and of ~28% for PF were noted. Among biomechanical variables, step frequency increased by ~2.7% and the ankle range of motion decreased by ~4.1% post-MUM. Runners adopting a non rearfoot strike pre-MUM adopted a less plantarflexed foot strike pattern post-MUM while those adopting a rearfoot strike pre-MUM tended to adopt a less dorsiflexed foot strike pattern post-MUM. Positive correlations were observed between percent changes in peripheral PF fatigue and the ankle range of motion. Peripheral PF fatigue was also significantly correlated to both percent changes in step frequency and the ankle angle at contact. This study suggests that in a fatigued state, ultratrail runners use compensatory/protective adjustments leading to a flatter foot landing and this is done in a fatigue dose-dependent manner. This strategy may aim at minimizing the overall load applied to the musculoskeletal system, including impact shock and muscle stretch.

Defining Off-road Running: A Position Statement from the Ultra Sports Science Foundation

“…In ultra-endurance running, V O 2max values in elite runners are similar to those observed in other elite endurance athletes (i. e. > 75 ml•kg − 1 •min − 1 and up to an extreme value of 92 ml•kg − 1 •min − 1 ) [53]. However, relatively low V O 2max values have also been observed thus far compared to other endurance sports (e. g. ranges between 45-60 ml•kg − 1 •min − 1 [19,[54][55][56][57][58]. It is recognised that V O 2max is positively related to ultra-endurance performance outcomes [55,56,59,60].…”

The role of the nervous system in neuromuscular fatigue induced by ultra-endurance exercise

“…Whether the greater voluntary activation reduction observed in PF is related to the extreme positive elevation change (+ 24 000 m) and/or the extreme duration (mean study participant race time = 122 h) of the race is unknown. Interestingly, changes to the foot strike pattern and running mechanics have been observed after a 110-km trail-running bout (Giandolini et al 2016) and the magnitude of these changes were related to the amount of peripheral fatigue. This suggests that in a fatigued state, ultratrail runners use compensatory and/or protective adjustments in a fatigue dose-dependent manner, to reduce the overall load applied to the musculoskeletal system (i.e.…”

Estudio del estado de fatiga en corredores de fondo a partir de patrones biomecánicos. Monitorización mediante sistemas integrados en el calzado

“…Existen dos interpretaciones sobre el efecto de la fatiga en relación a las fuerzas de reacción y el nivel de impactos durante la carrera (Giandolini et al, 2016).…”

“…En este sentido, varios estudios concluyen que no existen diferencias o en la magnitud del impacto o las fuerzas de reacción después de un ejercicio fatigante (Abt et al, 2011;Adam Clansey & Michael Hanlon, 2011; Adam Clansey, Michael Hanlon, Eric S. Wallace, & Mark J. Lake, 2012;Giandolini et al, 2016;Witzke et al, 2015).…”

“…En este sentido, Giandolini et al (2016) afirman que no parece existir una técnica de carrera (talonador o no-talonador) ideal en carreras de ultra distancia, y puede que la clave se halle en alternar el patrón con el fin de adaptarse a los factores tanto intrínsecos como extrínsecos. Por su parte encuentran diferencias en el movimiento de la cadera en corredores lesionados, pero no en corredores sanos.…”