Load And Speed But Not Footwear Increase Metabolic Rate And Carbohydrate Oxidation While Walking

PURPOSE: To compare metabolic rate () and substrate oxidation (respiratory exchange ratio [RER]) responses during motorized treadmill walking at incremental speeds with various load carriage and footwear configurations. METHODS: Nine subjects (male n = 7, 32 ± 9 y, height = 174.6 ± 5.1 cm, body mass (BM) = 75.44 ± 13.50 kg, O2max = 45.0 ± 3.5 mL.kg-1.min-1) walked three min at each speed (0.67, 1.12, and 1.56 m/s; 0% incline) in each of the following randomized iterations: sneakers without load, sneakers with load (22.5% BM), sneakers with heavy load (45% BM), military boots without load, military boots with load (22.5% BM), and military boots with heavy load (45% BM). During the last minute of each stage, expired gases were collected with net reported. Separate three-way repeated measures ANOVAs were used to determine changes in RER and across treadmill speed, footwear, and load carriage iterations (alpha = 0.05). RESULTS: No 3-way interactions were observed for RER (p = 0.19) or (p = 0.43). A speed by load interaction effect was observed for RER (p = 0.02) such that RER was highest at 1.56 m/s with 45% load (0.86 ± 0.08), 22.5% load (0.83 ± 0.05), and no load (0.82 ± 0.05) compared to 1.12 m/s with 45% load (0.81 ± 0.04), 22.5% load (0.80 ± 0.05), and no load (0.80 ± 0.05, all p ≤ 0.02) and 0.67 m/s with 45% load (0.80 ± 0.04), 22.5% load (0.79 ± 0.05), and no load (0.80 ± 0.05, all p ≤ 0.04). For , a speed by load interaction effect was observed (p < 0.01) whereby increased progressively with each increment of speed and load (0.67 m/s: no load, 1.78 ± 0.20 W/kg, 22.5% load, 2.15 ± 0.21, 45% load, 2.83 ± 0.24; 1.12 m/s: no load, 2.42 ± 0.20, 22.5% load, 3.08 ± 0.23, 45% load, 4.02 ± 0.26; 1.56 m/s: no load, 3.70 ± 0.41, 22.5% load, 4.91 ± 0.54, 45% load, 6.66 ± 0.77, [p < 0.01 for all]). Footwear had no effect on RER (p = 0.69) or (p = 0.20). CONCLUSION: Load carriage and walking speed have both independent and synergistic inflationary effects on metabolic rate that favor carbohydrate oxidation, without influence of footwear. The views expressed in this abstract are those of the authors and do not reflect the official policy of the U.S. Government, Department of Energy, Department of the Army, Department of Defense, or CoachMePlus. Funding provided through the Medical Technology Enterprise Consortium (#W81XWH-22-9-0014). Supported by: University at Buffalo Experiential Learning Network Grant