Metabolic, cardiovascular, neuromuscular and perceptual responses to repeated military-specific load carriage treadmill simulations.

Abstract

Bouts of military load carriage are rarely completed in isolation; however, limited research has investigated the physiological responses to repeated load carriage tasks. Twelve civilian men (age, 28±8years; stature, 185.6±5.8cm; body mass 84.3±11.1kg and maximal oxygen uptake, 51.5±6.4mL·kg-1min-1) attended the laboratory on two occasions to undertake a familiarisation and an experimental session. Following their familiarisation session, participants completed three bouts of a fast load carriage protocol (FLCP; ∼65min), carrying 25kg, interspersed with a 65-min recovery period. Physiological strain (oxygen uptake [V̇O2] and heart rate [HR]) was assessed during the FLCP bouts, and physical performance assessments (weighted counter-movement jump [wCMJ], maximal isometric voluntary contraction of the quadriceps [MIVC] and seated medicine ball throw [SMBT]) was measured pre and post each FLCP bout. A main effect for bout and measurement time was evident for V̇O2 and HR (both p<0.001 and Ѡ2=0.103-0.816). There was no likely change in SMBT distance (p=0.201 and Ѡ2=0.004), but MIVC peak force reduced by approximately 25% across measurement points (p<0.001 and Ѡ2=0.133). A mean percentage change of approximately -12% from initial values was also evident for peak wCMJ height (p=0.001 and Ѡ2=0.028). Collectively, these data demonstrate that repeated FLCP bouts result in an elevated physiological strain for each successive bout, along with a substantial reduction in lower body power (wCMJ and MIVC). Therefore, future research should investigate possible mitigation strategies to maintain role-related capability.