Effect of a load distribution system on mobility and performance during simulated and field hiking while under load.

ABSTRACT

This study was conducted to test a modular scalable vest-load distribution system (MSV-LDS) against the plate carrier system (PC) currently used by the United States Marine Corps. Ten Marines engaged in 1.6 km load carriage trials in seven experimental conditions in a laboratory study. Kinematic, kinetic, and spatiotemporal gait parameters, muscle activity (electromyography), heart rate, caloric expenditure, shooting reaction times, and subjective responses were recorded. There was lower mean trapezius recruitment for the PC compared with the MSV-LDS for all conditions, and muscle activity was similar to baseline for the MSV-LDS. Twenty-seven Marines carrying the highest load were evaluated in the field, which measured an increase in energy expenditure with MSV-LDS; however, back discomfort was reduced. The field evaluation showed significantly reduced estimated ground reaction force on flat-ground segments with the MSV-LDS, and the data suggest both systems were comparable with respect to mobility and energy cost. Practitioner summary: This study found that a novel load distribution system appears to redistribute load for improved comfort as well as reduce estimated ground reaction force when engaged in hiking activities. Further, hiking with a load distribution system enables more neutral walking posture. Implications of load differences in loads carried are examined. Abbreviations AGRF anterior-posterior ground reaction forces; CAREN Computer Assisted Rehabilitation Environment; GRF ground reaction forces; HR heart rate; ML-GRF mediolateral ground reaction forces; MOLLE Modular Lightweight Load-carrying Equipment; MSV-LDS modular scalable vest-load distribution system; NHRC Naval Health Research Center; PC plate carrier; PPE personal protective equipment; RPE rating of perceived exertion; SAPI small arms protective insert; sEMG surface electromyography; USMC United States Marine Corps; VGRF Ground reaction forces in the vertical.