Energy Expenditure When Walking While Wearing Either a Weighted Vest or a Loaded Backpack

Abstract

The use of a weighted vest has been advocated as a substitute to a weighted backpack for candidates completing emergency service physical employment standards tests as the weighted vests are considered more comfortable, result in a more upright walking posture and safer to wear. One assumption underpinning the loaded backpack test is that it incurs a rate of aerobic energy expenditure that is related to the aerobic energy demand of the relevant job. However, a change in load distribution may change the economy of movement and thereby alter the rate of aerobic energy expenditure required during the test. Therefore, a factor affecting the capacity to substitute a weighted vest for a loaded backpack is whether or not the wearing of the weighted vest incurs a different rate of aerobic energy expenditure to that incurred by wearing the loaded backpack. PURPOSE: To compare the rate of aerobic energy expenditure when walking while wearing a weighted vest compared to a loaded backpack. METHODS: Nine male and three females (mean ± SE: 25.4 ± 2.4 yr) completed two 4.83 km walking trials in random order at 6.44 km·hr-1 on a motor driven treadmill (0% grade) while wearing either a weighted vest or loaded backpack weighing 20.4 kg. All participants were experienced in wearing the two pieces of equipment. Oxygen uptake (VO2) was measured during min 1-3, 10-13, 20-23, 30-33 and 40-45 of each trial. Rate of aerobic energy expenditure was estimated by the mean of the five measurements. RESULTS: There was no significant difference (p=0.99; p=0.61 after adjustment for height, weight, age and gender) between the mean VO2 measured when the participants were wearing the weighted vest (1625.9 ± 36.4 mLO2·min-1) or the backpack (1625.6 ± 37.9 mLO2·min-1). However, there was a significant interaction between gender and load type (p=0.01), with mean VO2 being higher when wearing the vests in females and backpacks in males. Notwithstanding this interaction, ICC was 0.87 and Limits of Agreement were ±6% of the mean of all measurements. Systematic bias was 0.02%. CONCLUSION: The weighted vest and loaded backpack induced similar rates of aerobic energy expenditure in a standardised walking test. However, there was some evidence of a differential gender effect.