Influences of body composition upon the relative metabolic and cardiovascular demands of load-carriage.
OBJECTIVE
To test the hypothesis that measures of aerobic fitness, body mass and indices of body composition will influence the metabolic and cardiovascular demands of simulated load-carriage tasks.


METHODS
Twenty-eight healthy male volunteers, following assessment of maximal oxygen uptake (O(2)max) and body composition, walked on a treadmill at 4 kph (1.11 m/s) for 60 min on gradients of 0, 3, 6 and 9% whilst carrying backpack loads of 0, 20 and 40 kg. During the final 3 min of each 5-min exercise bout, indirect respiratory calorimetry and heart rate data were collected and the 'steady-state' metabolic O(2) and cardiovascular (heart rate) demands quantified.


RESULTS
Absolute O(2)max (ml/min) produced the strongest correlation (r = -0.64, P < 0.01) with the metabolic demand of heavy load-carriage (40 kg). The body composition index lean body mass/(fat mass + external load) produced a moderate correlation (r = -0.52, P < 0.01) with the metabolic demand of heavy load-carriage. The increases in metabolic and cardiovascular demands were greater when the load carried increased from 20 to 40 kg compared with 0 to 20 kg at all four gradients. A model incorporating anthropometric and physiological characteristics with gradient and load explains 89% of the variability in the metabolic demands of load-carriage compared with 82% using gradient and load alone.


CONCLUSIONS
The results show that indices of body composition as well as absolute aerobic power influence the relative metabolic demands of load-carriage. Application of these measurements would ensure selection criteria for load-carriage occupations are based on lean muscle mass rather than running speed.
Lyons
Jason
J
Institute of Naval Medicine, Environmental Medicine Unit, Alverstoke Gosport, Hampshire, UK. lyonsj@inm.mod.uk
Allsopp
Adrian
A
Bilzon
James
J
D000328:Adult; D001823:Body Composition / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology; D005080:Exercise Test; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D016014:Linear Models; D008297:Male; D010101:Oxygen Consumption / Q000502:physiology*; D016474:Weight-Bearing / Q000502:physiology*; D014938:Work Capacity Evaluation