Comparison of Ground Reaction Forces between Combat Boots and Sports Shoes

Abstract

It is unclear whether military shoes (combat boots and sports shoes) attenuate loading rate or affect force transfer during walking. Therefore, this study compared ground reaction forces (GRF) related to impact and force transfer between combat boots, military sports shoes, and running shoes. Ten army recruits walked over a walkway with two force plates embedded. GRF were measured when walking barefoot (for data normalisation) and with combat boots, military sports shoes, and running shoes. Loading rate, first and second peak forces, and push-off rate of force were computed along with temporal analysis of waveforms. Reduced loading rate was observed for the running shoe compared to the combat boot (p = 0.02; d = 0.98) and to the military sports shoe (p = 0.04; d = 0.92). The running shoe elicited a smaller second peak force than the combat boot (p < 0.01; d = 0.83). Walking with military shoes and combat boots led to larger force transfer than running shoes, potentially due to harder material used in midsole composition (i.e., styrene-butadiene rubber). Combat boots did not optimise load transmission and may lead, in a long-term perspective, to greater injury risk.

Influence of combat boot types on in-shoe forces and perceived comfort during unloaded and loaded walking

“…Two variables were chosen for analysis: (1) peak force, which was the maximum force value of each step taken, and (2) loading rate, calculated as the slope of vertical GRF from 20% to 80% of the time from initial contact to peak impact force. These types of GRF variables are commonly used to evaluate combat footwear during walking 10…”

“…One possible factor that may influence lower limb injuries is the choice of combat boots 10–13. While combat boots are essential protective gear for military personnel, it has been suggested that the poor shock absorption properties, poor fit and inadequate comfort of combat boots can be possible contributing factors to injuries 1 11.…”

“…Appropriate cushioning in footwear has been shown to improve shock absorption during locomotion,14 15 while inadequate cushioning properties were related to large impact forces acting on skeletal structures 9 16. Bini et al reported that walking with military shoes and combat boots led to larger force transfer than running shoes 10. The authors cautioned against a high injury risk in the long term since combat boots did not optimise the load transmission.…”

“…Most studies on combat boots were performed mainly in the Western demographics such as UK, Brazil, Australia and Cypriot 10 11 16 21 22. Their findings may not be directly applicable to Asians due to the foot structural differences such as wider feet and lower instep in Asians than Europeans 23.…”

“…Another consideration is the high loads of tactical equipment and body armour in combat training and field operations 21 24. Previous studies tend to focus on either loaded20 or unloaded10 11 14 22 walking, but biomechanical response and perceived comfort may vary with load carriage. Hence, there is a need to include both loaded and unloaded conditions in the same test protocol for comparison.…”