Physiological impact of load carriage exercise: Current understanding and future research directions

Abstract

Load carriage (LC) refers to the use of personal protective equipment (PPE) and/or load‐bearing apparatus that is mostly worn over the thoracic cavity. A commonplace task across various physically demanding occupational groups, the mass being carried during LC duties can approach the wearer's body mass. When compared to unloaded exercise, LC imposes additional physiological stress that negatively impacts the respiratory system by restricting chest wall movement and altering ventilatory mechanics as well as circulatory responses. Consequently, LC activities accelerate the development of fatigue in the respiratory muscles and reduce exercise performance in occupational tasks. Therefore, understanding the implications of LC and the effects specific factors have on physiological capacities during LC activity are important to the implementation of effective mitigation strategies to ameliorate the detrimental effects of thoracic LC. Accordingly, this review highlights the current physiological understanding of LC activities and outlines the knowledge and efficacy of current interventions and research that have attempted to improve LC performance, whilst also highlighting pertinent knowledge gaps that must be explored via future research activities.

Effect of the Law Enforcement Duty Belt on Muscle Activation during Hip Hinging Movements in Young, Healthy Adults

“…This suggests that dispersed loads, such as our vest condition, are perceived as more comfortable than centralized loads. However, body armor, such as a tactical vest, has been shown to be restrictive via reduced measures of mobility, physical performance, and necessary functions such as respiration [ 33 , 63 ]. This may be why some participants reported feeling more restricted in the vest condition versus the belt conditions.…”

The test–retest reliability of physiological and perceptual responses during treadmill load carriage

“…Load carriage is essential in physically demanding occupations such as the military and emergency services (Knapik et al 2004 ; Taylor et al 2016 ). Consequently, load carriage is an increasingly investigated research area due to both the importance and diverse nature of task requirements (Faghy et al 2022 ). Within the military, the type, amount, and distribution of equipment carried by personnel vary due to several factors including role, mission requirements, and environment.…”

Load carriage physiology in normoxia and hypoxia

“…Thoracic load carriage is an occupational requirement for many populations including search and rescue, military personnel, and wildland firefighters (Knapik et al 2004 ; Sol et al 2018 ; Faghy et al 2022 ). While necessary to fulfill operational duties, load carriage impairs exercise capacity and task performance (Knapik et al 1991 ; Holewun and Lotens 2007 ; Drain et al 2016 ).…”

“…The effects of load carriage on energy expenditure are well-documented, and numerous modeling equations have been developed to aid in operational planning (Pandolf et al 1977 ; Santee et al 2001 ; Looney et al 2018 ). In addition to energy cost, research has established that load carriage increases physiological strain, as recently reviewed (Faghy et al 2022 ). For example, load carriage has been reported to induce a shallower breathing pattern (i.e., reduced tidal volume [V T ] due to a reduced end inspiratory lung volume and increased breathing frequency [f B ]) leading to increased dead space ventilation (Phillips et al 2016b ).…”

“…However, it remains to be determined whether load carriage itself influences metabolism independent of environmental context. This is due to the fact that most load carriage studies employ designs that prevent detection of load carriage-specific effects, which may be expected given the above-described physiological strain imposed (Faghy et al 2022 ). Specifically, most prior load carriage studies that reported metabolic data either did not include an unloaded comparison condition (Griffiths et al 2019a ) or made comparisons to unloaded exercise based on matched walking speeds (Blacker et al 2009 ; Faghy et al 2016 ), which results in unequal VO 2 between conditions.…”