(42) AEROBIC FITNESS AND RELATIVE ARM MASS PREDICT SUSTAINABLE MILITARY LOAD CARRIAGE PERFORMANCE

Dismounted US Army Soldiers frequently carry excessively heavy loads (e.g. 66% body mass (BM)) during emergencies. Body composition and mass distribution may influence the maximal pacing individual Soldiers can sustain while carrying excessively heavy loads.

Purpose: Identify demographic, fitness, and body composition predictors to quantify maximal sustainable dismounted load carriage speed.

Methods: Forty-six US Army Soldiers and civilians (40 male, 6 female; mean ± SD;  age, 25 ± 8 y; height, 175 ± 8 cm; BM, 79 ± 15 kg) were assessed by dual-energy x-ray absorptiometry (DPX-IQ, Lunar Corporation, Madison, WI) and conducted incremental treadmill tests to determine their highest aerobically-sustainable walking pace (respiratory exchange ratio ≤ 1.0) while carrying an external load of 66% BM. Load carriage performance was predicted using a multiple linear regression model that included sex, age, height, BM, and maximal oxygen uptake (VO_2max) along with the type of load carrying equipment (military rucksack or weighted vest). We also included tissue types (lean, bone mineral content (BMC), fat) and regional masses (arms, legs, head, trunk) as percentages of BM to model body composition and mass distribution relationships, respectively.

Results: Peak sustainable walking speed was significantly higher when loads were carried by weighted vest versus rucksack (+0.54, ± 0.17 km/h; p =.003). Individual VO_2max and percentage arm mass had significant positive (p=.003) and negative (p=.032) relationships with peak speed, respectively.

Conclusions: Load distribution and aerobic fitness are two important predictors of maximal pacing for military personnel carrying emergency approach loads. Although impactful, arm mass is less important when carrying a proportionally sized load than other body regions responsible for loaded locomotion. PRACTICAL APPLICATIONS: Military leadership and personnel should focus training regimens on improving aerobic fitness and deemphasize upper body development to maximize load carriage performance.

The views expressed in this abstract are those of the authors and do not reflect the official policy of the U.S. Government, Department of Energy, Department of the Army, or Department of Defense.


Acknowledgements: None