Effects of Heavy Load Carriage during Constant-Speed, Simulated, Road Marching

Abstract

Load carriage is a key element in dismounted military operations. Load carriage requirements in the field regularly exceed 50% of lean body mass (LBM) and have only rarely been studied. Therefore, our purpose was to determine the metabolic and motivational effects of heavy loads (30-70% LBM) during constant-rate "road" marching on a treadmill. Ten healthy male Army officers carried loads of 30%, 50%, and 70% LBM in an all-purpose, lightweight, individual, carrying equipment pack for 30 minutes, at a speed of 6 km/h. Oxygen consumption (VO2), ventilation, heart rate (HR), respiratory exchange ratio, rating of perceived exertion (RPE), and Self-Motivation Inventory scores were recorded at each trial. Significant increases were observed for VO2, ventilation, and HR between the trials. RPE significantly increased for the 70% LBM trial, compared with the 30% and 50% trials. No significant differences were seen in respiratory exchange ratio or Self-Motivation Inventory scores. Increasingly heavy loads carried in a rucksack resulted in increased VO2, RPE, and HR; therefore, increasing the load that a soldier is required to carry may negatively affect road march performance.

Can load carriage system weight, design and placement affect pain and discomfort? A systematic review

“…Ling et al reported that level of discomfort increased as the load increased in adults [32]. Also, Beekley et al showed that perceived exertion was significantly higher while carrying 70% lean body mass (LBM) than 30% and 50% LBM in adults; however, no differences in perceived exertion responses were seen between 50% and 30% LBM [5]. Lloyd et al observed that pain, perceived exertion and regional discomfort increased with increasing load (from 10% to 70% of body mass) in most of the body parts while some other parts such as chest, hips, buttocks and feet only showed significant changes between 15% and 20% body mass load [33].…”

“…Subjects start to notice differences in sensation of effort at different load thresholds and also the level of pain and discomfort threshold varies among individuals. It seems that age, gender, the circumstances of the load carrying experience and profession are factors that have an effect on the load threshold [5].…”

“…From this review it became apparent that factors other than backpack weight can generate pain, perceived exertion or discomfort; the reported factors were gender [15,16,39,40,43,54], age and grade in school [2,15,39,48,54], subject's body mass index [5,47], the amount of time using the backpack and walking to and from school [10,41,47,48,53]. Girls experience more pain that boys, this could be because, boys have a stronger musculoskeletal system, also they might have higher threshold of pain based on differences between physiological and psychological factors between genders [46].…”

The Impact of Occupational Load Carriage on Carrier Mobility: A Critical Review of the Literature

“…Specialist police officers may likewise be required to carry loads that consist of body armour and vests and carry firearms and other specialized equipment, e.g., riot shields [3]. While research suggests that some specialist personnel are heavier, stronger, and fitter than their predecessors [4,5,6], the loads that these personnel are required to carry are likewise increasing [6,7,8]. As an example, during World War I, American and Australian military soldiers carried an average load of 30-40 kg [6], whereas during recent conflicts in Afghanistan, soldiers have carried an average load of 44-48 kg [6,9,10].…”

Loaded and Unloaded Marching: Implications for Fluid Replacement

“…The standard weight of load carriage has recently been reported to vary between 22-29 kg for a fighting load, 33-44 kg for an approach march load and 58 kg for an emergency approach march [1,2]. However, soldiers' loads frequently exceed these values, with over 60 kg being reportedly carried [1][2][3].…”