Energy cost of stepping in protective clothing ensembles

Abstract

This study investigated the effect of protective clothing ensembles (against chemical agent and cold weather) on the energy cost of a bench stepping task (20 steps/min on a 0·305 m high bench). Twelve male soldiers (mean age 25·5 years; mean weight 75·4 kg) performed the task at an ambient temperature of 10°C in each of the following clothing ensembles: A, military combat clothing; B, as A plus chemical agent protective clothing; C, as B plus long underwear and quilted thermal jacket liner, D, as C plus quilted thermal trouser liners. Determinations were made of oxygen consumption ([Vdot]O₂) (as a measure of energy cost), heart rate (HR) and subjective rating of perceived exertion from the Borg scale (RPE). All variables showed a clear trend towards increasing with the amount of clothing worn and were significantly increased by the protective clothing ensembles (B, C and D). [Vdot]O₂(1/min)was 1·85,1·99,2·05 and 2·13 during stepping in Ensembles A, B, C and D, respectively. These increases were proportionately greater than the increases in clothing weight and external workrate. As a result, when corrected for clothed weight, [Vdot]O₂ was greater by an average of 9% in Ensemble D than in ensemble A. This indicates that prediction of [Vdot]O₂ from external workrate will yield erroneous data for subjects wearing protective clothing ensembles. When protective clothing ensembles are worn, the increased energy cost of physical performance will reduce the time to the onset of fatigue and, because of the increased metabolic heat production, could exacerbate problems of heat dissipation and thus increase the risk of overheating. These factors should be taken into account when work must be undertaken in conditions demanding the use of such clothing.