Effects of leg fatigue due to exhaustive stair climbing on gait biomechanics while walking up a 10˚ incline – implications for evacuation and work safety

This biomechanics study explored stride length (SL), duration (SDN), and gait ground reaction forces (GRFspeak), required coefficient of friction (RCOFpeak), joint angle (anglepeak, anglemin), angular velocities (angvelx peak), angular accelerations (angaccx peak), muscle electromyography (EMG) during the dominant leg stance phase (SP) following an exhaustive stair ascent for evacuation. Data were collected by a three-dimensional motion capture system synchronized with EMG and force plate when walking upwards on a 10° inclined walkway.The significantly (p≤0.05) decreased EMG median frequencies of tibialis anterior during early (ES) and late stance (LS) phases, and vastus lateralis muscles during LS are the evidence of leg local muscle fatigue (LMF). The perpendicular and longitudinal shear GRFspeaks were significantly reduced during ES (p≤0.05) and LS (p≤0.01), respectively. The post-fatigue SP, SL, and SDN were significantly (p<0.05) shorter. Specially, the foot anglemins, ankle anglepeaks, and relevant angvelx peaks, and angaccx peaks significantly (p≤0.05) decreased in post-fatigue trials. The post-fatigue RCOFpeaks were found significantly (p≤0.01) lower during LS phase. Thus, whole body exhaustion and leg LMF constrained the gait kinetics and kinematics when walking upwards indicating a cautious gait associated with the risks of falls, accidents, which can hinder the process of evacuation and work safety on slopes.