Comparison of five modes of carrying a load close to the trunk†

Abstract

This study was designed to investigate the cardiorespiratory, metabolic, and subjective responses to carrying a load close to the trunk in five different ways. Each of five subjects carried a load equivalent to 35% body weight (BW) for one hour at 4-5 km hr⁻¹ and 0%grade on a motor driven treadmill using each of the following modes of load carriage: (1) the total load carried in a backpack with frame (BP/F), (2) the total load carried in a backpack with no frame (BP/NF), (3) half the load in a backpack (with frame) and half in pouches attached to a waist belt (BP/WB), (4) half the load in a backpack (with frame) and half in a front pack on the chest (BP/FP), and (5) the total load carried as a trunk jacket (TJ), i.e. a military type ‘flak’ jacket with weights inserted in pockets evenly distributed about the trunk. There were no statistically significant differences in the mean cardiorespiratory and metabolic costs associated with each of the five modes of load carriage. However, BP/FP and TJ were subjectively rated as significantly (P < 001) more comfortable than BP/F and BP/NF, suggesting that there may be physiological differences between the five modes of load carriage which were not detected by the cardiorespiratory and metabolic measurements used in this study (i.e. heart rate, oxygen consumption and minute ventilation). In contrast, the BP/FP was reported to be the hardest to don and doff and was associated with a statistically significant (P <0-05) restrictive type of ventilatory impairment. In conclusion, in practical terms there may seldom be a single ‘best’ way to carry a 35% BW load close to the trunk.