Tibialis anterior muscle fatigue leads to changes in tibial axial acceleration after impact when ankle dorsiflexion angles are visually controlled

Abstract

Heel impact forces may lead to injury as they travel through the human musculoskeletal system. Previous work on the effect that localized muscle fatigue has on the tibial response (shank axial acceleration) to impact was limited because ankle angle was not controlled. The purpose of this study was to compare the tibial response when the tibialis anterior was fatigued and when not fatigued, while participants controlled dorsiflexion angles at impact using visual feedback. Twenty participants (10 male, 10 female; M ± SD = 21.8 ± 2.9 years) were strapped supine to a human pendulum apparatus, and instrumented with a low mass accelerometer (affixed medial to the tibial tuberosity). Participant dorsiflexion angle range was recorded by an electro-goniometer, and divided into four angle ranges so tibial response variables (peak tibial acceleration, time to peak acceleration, acceleration slope) could be compared when fatigued and not fatigued. Peak tibial acceleration and acceleration slopes decreased, and time to peak acceleration increased following fatigue, when comparing values across the same dorsiflexion ranges. Dorsiflexion angle alone did not account for differences in tibial response during localized leg muscle fatigue; supporting prior work and suggesting that the muscle and ankle joint become less stiff when fatigued, thereby increasing the lower extremity attenuation capability to heel impacts.