The Effects of Military-Style Load Carriage on Upper Limb Performance, Biomechanics and Hemodynamics

Military personnel and day hikers carry loads of 40% or more of their body weight (BW) in backpacks. This load carriage can result in loss of sensation and function in the upper limb. There have been few studies on the effects of military load carriage on the upper extremity Purpose: This study aimed to evaluate the effects of military-style load carriage on the biomechanics, motor performance and blood flow of the upper limbs. Methods: Fifteen healthy male subjects (26 ± 6.6 years, 175.20 ± 6.200 cm, 79.86 ± 12.003 kg) participated in 3 conditions: no load, walking with a backpack loaded to 40% BW (BP), and walking with a loaded backpack and a baseball bat to simulate rifle carriage (BRC). For each condition pinch strength, grip strength, light touch threshold, blood flow volume, a timed grooved pegboard test, and a timed two-hand placement test for motor performance was measured. Subjects performed all measurements immediately before and after a 45-minute treadmill walking trial and then again after a 10-minute seated recovery, with no backpack on. Perceived measures were taken during the walking trial every 15 minutes for a total of 3 time points. Results: Pinch strength and the grooved pegboard completion times were significantly affected (p0.05), in a detrimental manner, by walking with 40% BW load carriage. Blood flow volume was significantly decreased (p≤0.001) in both the BP and BRC conditions immediately after the backpack was donned and then increased back to baseline after the walking trial. Both BP and BRC conditions also resulted in increased exertion, as well as increased pain and/or discomfort at the shoulders and the upper trapezius. However, no significant effect was found for grip strength or sensory threshold changes among conditions or time points. Conclusion: Implications for those who carry heavy backpacks are that pinch strength, fine motor tasks and blood flow may be affected, but other upper limb function remained unaffected after load carriage.