Impact of carrying heavy loads on postural sway and relative ground reaction forces during quiet stance in intervention police officers

Abstract

Although carrying heavy loads impacts gait characteristics in military personnel, less studies have examined whether a gradually load increase affects foot parameters during quiet standing in the different population of intervention police officers. Therefore, the main purpose of the study was to examine differences in postural sway and ground reaction force characteristics during a quiet stance while carrying progressively heavier equipment. Ninety-six elite intervention male police officers were assessed under four conditions: (i) ‘no load’, (ii) ‘a 5 kg load’, (iii) ‘a 25 kg load’, and (iv) ‘a 45 kg load’. Foot characteristics during standing were assessed with the Zebris pedobarographic pressure platform. Heavier loads increased 95% confidence ellipse area (p=.012, η2=0.028), the center of pressure path length (p=.010, η2=0.029) and average velocity (p=.011, η2=0.029), and length of the minor (p<.001, η2=0.040) and major axis (p=.004, η2=0.035). No significant changes in relative ground reaction forces beneath the forefoot and hindfoot regions of both feet were observed (p>.05). The findings suggest that spatial and temporal foot parameters may be more prone to change while carrying heavy loads, especially the center of pressure characteristics.