Abstract
BackgroundThe tibialis posterior muscle is believed to play a key role in controlling foot mechanics during the stance phase of gait. However, an experiment involving localised tibialis posterior muscle fatigue, and analysis of discrete rearfoot and forefoot kinematic variables, indicated that reduced force output of the tibialis posterior muscle did not alter rearfoot and forefoot motion during gait. Thus, to better understand how muscle fatigue affects foot kinematics and injury potential, the purpose of this study was to reanalyze the data and investigate shank, rearfoot and forefoot joint coupling and coupling variability during walking.MethodsTwenty-nine participants underwent an exercise fatigue protocol aimed at reducing the force output of tibialis posterior. An eight camera motion analysis system was used to evaluate 3 D shank and foot joint coupling and coupling variability during treadmill walking both pre- and post-fatigue.ResultsThe fatigue protocol was successful in reducing the maximal isometric force by over 30% and a concomitant increase in coupling motion of the shank in the transverse plane and forefoot in the sagittal and transverse planes relative to frontal plane motion of the rearfoot. In addition, an increase in joint coupling variability was measured between the shank and rearfoot and between the rearfoot and forefoot during the fatigue condition.ConclusionsThe reduced function of the tibialis posterior muscle following fatigue resulted in a disruption in typical shank and foot joint coupling patterns and an increased variability in joint coupling. These results could help explain tibialis posterior injury aetiology.
Highlights
The tibialis posterior muscle is believed to play a key role in controlling foot mechanics during the stance phase of gait
Biomechanical research conducted on patients with posterior tibialis tendon dysfunction (PTTD) highlights the importance of this muscle in controlling rearfoot, midfoot, and forefoot mechanics during gait [19,20,21]
Eight participants did not drop below the predetermined threshold of 70% baseline MVIC but were still included in the analysis since they were unable to complete two additional sets of 50 repetitions due to muscle fatigue and exhibited a 21% reduction in force output
Summary
The tibialis posterior muscle is believed to play a key role in controlling foot mechanics during the stance phase of gait. Biomechanical research conducted on patients with posterior tibialis tendon dysfunction (PTTD) highlights the importance of this muscle in controlling rearfoot, midfoot, and forefoot mechanics during gait [19,20,21]. These studies involved patients with moderate- to advanced-stage PTTD and may not provide adequate information to help us understand the contribution that the tibialis posterior muscle plays in controlling foot pronation in healthy individuals
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