Energy cost, perceived exertion and postural adjustments when treadmill walking with two types of backpack

This study prospectively examined energy expenditure and postural alterations resulting from load carriage on eleven volunteers from the Northern Arizona University community. Exclusion criteria included orthopedic or cardiovascular pathologies that may influence their ability to walk on a treadmill. Subjects were videotaped in the exercise physiology laboratory while walking at 1.43m/sec on a treadmill at 0%, 5% and 10% grade wearing no pack, a waist pack or a shoulder pack loaded with 4.52kg in random order. Energy expenditure was measured quantitatively using expired gasses and qualitatively using the Borg perceived exertion scale. Videotape images were analyzed for trunk, hip, knee and ankle angles. Significant differences in VO₂ existed between the levels of grade and between the no pack condition and either pack, but no differences were found between packs. The rates of perceived exertion increased with increasing grade and between load and no load, but no difference was found between packs. Significant postural adjustments at heel strike occurred with increases in grade, but no differences were found between packs or in the presence of a load or no load. We conclude that when pack loads are light, the metabolic and biomechanical consequences of pack choice are negligible.