Physiological Demands and Characteristics of Movement During Simulated Combat.

Introduction: Military tasks place considerable physiological demands on the soldier. It is therefore important to know the energy expenditure of soldiers while solving tasks in different environments. The purpose of this study was to describe the cardiorespiratory demands of certain movements and activities on ground combat soldiers during military field operations using body sensors and simulated combat.

Materials And Methods: Movement characteristics and cardiorespiratory responses were assessed in 42 soldiers (three women) in the Swedish Army. The different posts assessed were commander, combat engineer, driver, and gunner. The military field exercises examined were urban operations and retrograde operations in rough terrain. Measurements included (1) body mass, (2) heart rate (HR) including maximal (HRmax), (3) velocity, (4) accelerations/decelerations, and (5) distance moved. Maximal aerobic capacity (V̇O2peak, mL·kg-1·min-1) was tested in a laboratory setting when wearing combat gear and body armor.

Results: There was a weak positive correlation (r = 0.41 and 0.28, both P < .05) between VO2peak and percentage of time over 40% and 50% of maximal aerobic capacity during simulated combat. No differences were found for the different posts in time spent over 40% or 50% of maximal aerobic capacity and 76% of their HRmax (P > .05). Wearing combat gear and additional load while solving tasks resulted in mean HR varying between 98 and 111 beats·min-1, corresponding with 50-57% of the soldiers HRmax. Studying all exercises, mean HR was 105 ± 11 beats min-1, 54 ± 5% of HRmax corresponding to light work intensity. Soldiers performed between 2.8 and 4.9 accelerations/min in the different exercises. A significant correlation between V̇O2peak (mL kg-1 min-1) and acceleration and m/min were found, implying that soldiers with good aerobic capacity were able to cope better with tasks requiring quick movements.

Conclusion: Conducting military operations in urban terrain and retrograde operations in rough terrain strains ground combat soldiers' cardiorespiratory system, with work intensities close to 40% of maximal aerobic capacity in 15-33% of mission time. Tasks with external load carriage include change of direction, accelerations, bounds, and jumping over obstacles, and physical fitness tests should replicate this. Findings in this study also add objective data to the physiological demands of work performed by combat soldiers while conducting urban operations and retrograde operations in rough terrain. These findings could be used to develop a model for classifying work demands for ground combat forces.