Metabolic Cost and Fuel Utilization of Normal and Lower Body Positive Pressure Treadmill Running

Abstract

Lower body positive pressure (LBPP) treadmill walking and running are being used more frequently in clinical and athletic settings. Accurate exercise intensity and knowledge of fuel utilization is a needed for proper exercise prescription especially for obese patients that may benefit from LBPP exercise. It is unclear if current ACSM metabolic equations are suitable for LBPP running. There are currently no accepted calculations to estimate caloric cost or exercise intensity for LBPP running. PURPOSE: To measure oxygen uptake and caloric expenditure of treadmill running at normal body weight and LBPP. METHODS: Thirteen physically active non-obese participants completed four bouts of running exercise in a counterbalanced manner: (a) running on a normal (100% body weight, BW) treadmill (TM) and (b) running on a LBPP treadmill at 40, 60, and 85% of BW for 4 min intervals. Oxygen consumption was measured using open flow indirect calorimetry (Medgraphics Ultima) and last minute averages were defined as steady state. RESULTS: Volunteers’ average (±SD) absolute VO2 at a treadmill speed of 3.13 m·s-1 was 1528.38±308.38,1762.00±341.57, 2037.07±337.47, and 2453.23±406.49 ml·min-1 for 40, 60, 85, and 100% body weight. Respiratory exchange ratio (RER) at a treadmill speed of 3.13 m·s-1 was 0.91±0.05, 0.93±0.08, 0.98±0.05, and 1.02±0.07 for all four weighted conditions (40, 60, 85, and 100% BW, respectively). Average caloric expenditure was 7.55±1.51, 8.74±1.74, 9.51±1.72, and 12.43±2.01 kcal·min-1 for 40, 60, 85, and 100% BW, respectively. CONCLUSION: As expected, treadmill running in LBPP resulted in significantly lower oxygen consumption and caloric expenditure at all three reduced weight conditions compared to 100% BW. One-way repeated measures ANOVAs indicated statistically significant differences in VO2 across all four BW conditions F(3,36) = 64.636, p < 0.05, partial η2 = 0.843, and in caloric expenditure F(3,36) = 81.460, p < 0.05, partial η2 = 0.872. The percent difference in VO2 from TM and LBPP conditions (85, 60, and 40% of BW) was only ~15, 30, and 40%. We conclude that metabolic cost of LBPP running is significantly less than normal treadmill running, yet the decrease in VO2 and caloric expenditure is not as great as predicted by the change in body mass.