Grade and Weighted Vest Effects on Rate of Walking Energy Expenditure

Abstract

Walking is a low energy cost leisure time physical activity requiring greater frequency and longer duration to yield health benefits. Increasing the rate of energy expenditure of walking would favorably affect time as a constraint/barrier to participation while improving its use for weight control. PURPOSE: To examine the effects of changing grade and using a weighted vest (WV) on metabolic costs and cardiorespiratory responses to walking. METHODS: Following a maximal treadmill walking test, fifteen (11 females, 4 males) above average aerobically fit (VO2max = 47.5 ± 9.8 mL O2/kg/min) college-aged (20 ± 1.4 yr) volunteers participated in four different 10 minute sub maximal exercise sessions, on separate occasions. Subjects walked on a treadmill at 3.5 mph, 0% grade (baseline (B)); 3.5 mph + and −5% grade; and 3.5 mph, 0% grade while wearing a 20 lb weighted vest. Heart rate (HR) via Polar monitor and oxygen consumption (VO2) were continuously measured to establish steady state conditions. Thermal equivalents of oxygen were determined using nonprotein RQ. Statistical analyses included ANOVA with repeated measures and significance level set at .05. RESULTS: Mean oxygen uptake values for uphill (+5% grade) and weighted walking were significantly greater than baseline while downhill (−5% grade) values were not significantly different from the flat grade values (B = 16.8 + 2.4;+5% = 23.2 +2.9; WV= 18.5 +2.3; −5% = 15.5 +2.2 mL O2/kg/min). Kcal/min expenditures were: B = 5.83; +5% = 7.89; −5% = 5.26; WV = 6.48. HR (bpm) was significantly higher for +5% grade (139.7 + 24.2) and weighted walking (125.6 + 22.1) compared to baseline (119.7 ± 22.8). Downhill (−5%) walking HR (110.3 + 20.9 bpm) was significantly lower than flat grade baseline HR. CONCLUSIONS: These findings support positive graded walking as an effective way to increase the rate of energy expenditure of walking (60 kcal more per 30 min compared to walking on a flat grade at the same speed) and are consistent with “moderate” relative intensity CDC/ACSM recommendations. HR was 70% of age predicted HRmaxfor uphill walking but only 60% for flat grade walking. Each of the other treatment conditions was “light” in relative intensity with WV borderline “moderate” intensity (63% of age predicted HRmax) and 20 kcal greater expenditure for 30 min than baseline.