Muscle Activity during Postural Stability Tasks: Role of Military Footwear and Load Carriage

Abstract

<jats:p>Decrements to postural control manifest as an increase in muscle activity, indicating continuous attempts to maintain body equilibrium and postural stability. Extrinsic factors such as footwear, and intrinsic factors such as muscle fatigue, can affect postural stability. The purpose of this study was to analyze the impact of two types of military footwear and a military-type load-carrying task on lower extremity muscle activity during various postural stability tasks. Sixteen males’ (age: 26.63 ± 3.93 years; mass: 87 ± 12.4 kg; height: 178.04 ± 6.2 cm) muscle activity from knee flexors, extensors, ankle dorsiflexors, and plantar flexors were measured using electromyography in standard (STD) and minimalist (MIN) military footwear, before (PRE) and after (POST) a simulated workload during sensory organization and motor control tests on the Neurocom EquitestTM. Mean muscle activity was analyzed using 2 (footwear) × 2 (time) repeated measures ANOVA with an alpha level of 0.05. Results revealed a requirement of significantly greater muscle activity in POST and STD. MIN demonstrated lesser balance decrements POST workload, which could be attributed to its design characteristics. Results will help in suggesting footwear design characteristics to minimize muscular exertion while eliciting better postural control, and to prevent postural instability due to overexertion in military personnel.</jats:p>

Impact of Prolonged Exposure to a Slippery Surface on Postural Stability

“…These affected receptors impair the somatosensory feedback to the postural control system causing balance decrements. This impact on the afferent system manifests as higher muscle activity, indicating greater muscle activity requirement for postural control with fatigue [ 36 ]. Thus, the balance decrements observed in the study could be attributed to the undue fatigue caused by anterior load carrying and prolonged walking.…”

“…A lower amount of friction between the slippery surface and the participants’ shoes causes constant perturbations, requiring the postural control system to continuously correct the participants’ posture. Moreover, it is shown that the individuals acquire certain adjustments to the spatiotemporal parameters of gait during anticipated or encountered slips [ 33 , 36 ]. Thus, the balance decrements on the slippery surface could have occurred due to the anticipatory or reactive gait modifications that were acquired to minimize slipping [ 38 ].…”

Role of Occupational Footwear and Prolonged Walking on Lower Extremity Muscle Activation during Maximal Exertions and Postural Stability Tasks

“…Several previous studies in the literature have reported the impact of extrinsic factors, such as occupational footwear and the impact of intrinsic factors such as muscular fatigue, on postural control and stability. Postural stability has been reported to be impacted by occupational footwear such as work boots [2][3][4][5], firefighter boots [6,7], and military boots [8][9][10][11] when exposed to various simulated occupational workloads. As such, muscular fatigue quantified by torque [6], muscle activity through electromyography (EMG) measures during postural stability tasks, but only after a fatiguing workload [10,12], perceived exertion [5,10,13], and increased energy expenditure [14] have been reported due to occupational footwear type and workload type.…”