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

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.

Factors Affecting Performance on an Army Urban Operation Casualty Evacuation for Male and Female Soldiers

INTRODUCTION

This study was conducted to determine what physical and physiological characteristics contribute to the performance of an urban operation casualty evacuation (UO) and its predictive test, FORCE combat (FC) and describe the metabolic demand of the UO in female soldiers.

METHODS

Seventeen military members (9 M and 8 F) completed a loaded walking maximal aerobic test, the UO and FC. Heart rate reserve (HRR) and completion time were used as efficiency/performance measures. Oxygen consumption (VO2) was directly measured for UO on five female participants with a portable indirect calorimetry system, and analyzed using descriptive statistics. Stepwise multiple regression analysis was used to determine the contribution of the non-modifiable (age, sex, height) and modifiable characteristics (lean body mass to dead mass ratio (LBM:DM), VO2max corrected for load (L.VO2max), peak force (PF) measured on an isometric mid-thigh pull (IMTP) and medicine ball chest throw distance (Dist) on to the performance of each exercise.

RESULTS

LBM:DM and PF were the only factors included in the stepwise regression model for UO, predicting 70% of UO performance (p < 0.01). For FC, L.VO2max only was included in the stepwise regression model predicting 54% of FC performance (p < 0.01). Sex, age and height were not included in the regression model. The average metabolic cost of UO was 21.4 mL of O2*kg-1*min-1 in female soldiers while wearing PPE.

CONCLUSION

This study showed that modifiable factors such as body composition, PF on IMTP and L.VO2max are key contributors to performance on UO and FC performance.

An Occupational-Specific O2max Protocol for Structural Firefighters

OBJECTIVE

The aim of this study was to validate a (Equation is included in full-text article.)O2max protocol designed specifically for the occupational demands of firefighters by incorporating the use of personal protective equipment (PPE).

METHODS

Career firefighters completed a stage-graded exercise test (GXT) with submaximal square-wave verification bout while wearing PPE (pants and boots) to determine (Equation is included in full-text article.)O2max. Using the self-reported Physical Activity-Rating (PA-R) scale and an estimated nonexercise regression equation of (Equation is included in full-text article.)O2max for comparison to measured.

RESULTS

Twenty-eight male, career firefighters performed the GXT and square-wave bout. (Equation is included in full-text article.)O2 values (mean ± SD) from the GXT and the square-wave verification bout were 41.04 ± 6.98 and 39.74 ± 6.42 mL/kg/min, respectively (ICC = 0.98, typical error = 0.96 mL/kg/min, CV = 2.4%).

CONCLUSION

Our data suggest an incremental treadmill protocol that incorporates PPE and square-wave verification as an occupational-specific tool to measure cardiovascular fitness in firefighters.