Influence of military-type workload and footwear on muscle exertion during static standing

Abstract

Lower extremity muscular exertion and footwear design characteristics during a physiological workload have been shown to influence muscle activity. However, a dearth in the literature remains on muscular activation and exertion influenced by different military footwear when exposed to a military-type workload during static standing. The purpose of the study was to assess lower extremity muscular activity during erect standing, before (PRE) and after (POST) a military workload, in two military footwear [standard tactical (STD), minimalist (MIN)]. Twenty-two recreationally trained males (age: 22.1 § 2.1 years; height: 176.6 § 6.8 cm; mass: 79.8 § 9.7 kg) were tested, following a repeated measures counterbalanced footwear assignment. Participants performed maximal voluntary isometric contractions (MVICs) and bilateral static balance assessments before and after a 16-kg load-carrying treadmill workload. Electromyography (EMG) muscle activity was collected during the postural control tasks on ankle dorsiflexors, plantar flexors, inverters and everters in pre-workload and post-workload conditions. Dependent EMG variables of mean, peak, root-mean square, percent MVIC and co-contraction index were calculated and analyzed with a 2 £ 2 within-subjects repeated measures analysis of variance with the alpha level set p < 0.05. Pre-workload muscle activity did not differ between footwear. However, MIN demonstrated lower muscle activity during post-workload static standing. Additionally, a shorter workload time was recorded while donning STD compared to MIN. In acute conditions, lower extremity muscle activity does not differ between the military footwear. However, after undergoing an occupation-related workload, standard tactical footwear increases muscle exertion, thus suggesting a diminished effect on lower extremity muscle activity.