Abstract
BackgroundThe purpose of this study was to investigate the effect of localised tibialis posterior muscle fatigue on foot kinematics during walking. It was hypothesised that following fatigue, subjects would demonstrate greater forefoot and rearfoot motion during walking. It was also postulated that the magnitude of the change in rearfoot motion would be associated with standing anatomical rearfoot posture.MethodsTwenty-nine subjects underwent an exercise fatigue protocol aimed at reducing the force output of tibialis posterior. An eight camera motion analysis system was used to evaluate 3D foot kinematics during treadmill walking both pre- and post-fatigue. The anatomical rearfoot angle was measured during standing prior to the fatigue protocol using a goniometer.ResultsPeak rearfoot eversion remained unchanged following the fatigue protocol. Although increases in rearfoot eversion excursion were observed following fatigue, these changes were of a magnitude of questionable clinical significance (<1.0°). The magnitude of the change in rearfoot eversion due to fatigue was not associated with the anatomical measurement of standing rearfoot angle. No substantial changes in forefoot kinematics were observed following the fatigue protocol.ConclusionsThese data indicate that reduced force output of the tibialis posterior muscle did not alter rearfoot and forefoot motion during gait. The anatomical structure of the rearfoot was not associated with the dependence of muscular activity that an individual requires to maintain normal rearfoot kinematics during gait.
Highlights
The purpose of this study was to investigate the effect of localised tibialis posterior muscle fatigue on foot kinematics during walking
Subjects Based on a within group standard deviation of 5.5° and an expected 15% difference between pre and post measures, α = 0.05, β = 0.80, we found that 28 subjects were needed to provide sufficient power for this study
Following the fatiguing exercise protocol the mean MVC force output dropped to 44.6 N (21.8) which equated to 67% of the pre-fatigue baseline value
Summary
The purpose of this study was to investigate the effect of localised tibialis posterior muscle fatigue on foot kinematics during walking. Cadaveric studies have demonstrated that muscles assist in maintaining both rearfoot and midfoot posture [4,5], little research has been conducted regarding the in-vivo contribution of muscular activity to controlling foot pronation during gait. The tibialis posterior is believed to play a key role as an invertor of the rearfoot [6] in addition to providing dynamic support across the midfoot [4,5]. Research has shown that selective activation of tibialis posterior was better achieved using closed chain resisted foot adduction as opposed to open chain supination [11]. To better understand the role of tibialis posterior fatigue on foot mechanics it seems prudent to use an exercise that more selectively activates this muscle
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