Energy cost and mechanical work of walking during load carriage in soldiers.
In the military context, soldiers carry equipments of total mass often exceeding 30%-40% of their body mass (BM) and complexly distributed around their body (backpack, weapons, electronics, protections, etc.), which represents severe load carrying conditions.


OBJECTIVE
This study aimed to better understand the effects of load carriage on walking energetics and mechanics during military-type walking.


METHODS
Ten male infantrymen recently retired from the French Foreign Legion performed 3-min walking trials at a constant speed of 4 km·h(-1) on an instrumented treadmill, during which walking pattern spatiotemporal parameters, energy cost (C(W)), external mechanical work (W(ext)), and the work done by one leg against the other during the double-contact period (W(int,dc)) were specifically assessed. Three conditions were tested: (i) light sportswear (SP, reference condition considered as unloaded), (ii) battle equipment (BT, ∼22 kg, ∼27% of subjects' BM, corresponding to a military intermediate load), and (iii) road march equipment (RM, ∼38 kg, ∼46% of subjects' BM, corresponding to a military high load).


RESULTS
Repeated-measures ANOVA showed that military equipment carriage significantly (i) altered the spatiotemporal pattern of walking (all P < 0.01), (ii) increased absolute gross and net CW (P < 0.0001), and (iii) increased both absolute and mass-relative W(ext) (P < 0.01) and W(int,dc) (P < 0.0001) but did not alter the inverted pendulum recovery or locomotor efficiency.


CONCLUSIONS
Military equipments carriage induced significant changes in walking mechanics and energetics, but these effects appeared not greater than those reported with loads carried around the waist and close to the center of mass. This result was not expected because the latter has been hypothesized to be the optimal method of load carriage from a metabolic standpoint.
Laboratory of Exercise Physiology (EA4338), Saint-Etienne, France. jordane.grenier@gmail.com
Jordane G
JG
Grenier
Nicolas
N
Peyrot
Josiane
J
Castells
Roger
R
Oullion
Laurent
L
Messonnier
Jean-Benoit
JB
Morin
D000328:Adult; D000704:Analysis of Variance; D001696:Biomechanical Phenomena; D015992:Body Mass Index; D002153:Calorimetry, Indirect; D004734:Energy Metabolism / Q000502:physiology*; D006801:Humans; D008297:Male; D008889:Military Personnel; D010101:Oxygen Consumption / Q000502:physiology; D016138:Walking / Q000502:physiology*; D016474:Weight-Bearing / Q000502:physiology*