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Physiological Responses During A Modified Bruce Max Test In The Anti-Gravity Treadmill
INTRODUCTION: Physical activity can be difficult or painful for the obese, disabled, or those recovering from injury or surgery. For all populations, regular physical activity is a necessity for overall health, increased mobility, and reduction of all-cause mortality rates. Lower body positive pressure (LBPP) treadmills offer a way to unweigh users in an effort to reduce reaction forces that may inhibit physical activity and are less painful than traditional harness systems. To address this, the physiological responses in the AlterG© Anti-Gravity treadmill were measured, while performing a modified Bruce max test. The measurements take were the RPE, absolute and relative maximal oxygen consumption, heart rate, and respiratory exchange ratio of 3 males and 2females during an exercise test using a modified Bruce protocol on at 100 and 70 percent body weight. The last variable measured was the time it took to get to maximal aerobic capacity. PURPOSE: The purpose of this study was to determine whether there would be any significant differences in metabolic work to maximal aerobic capacity on an anti-gravity treadmill, using differential air pressure, at different percentages of body weight (100% and 70%). The null hypothesis is that there is no significant difference in physiological responses between different percentages of body weight as measured by RPE, absolute and relative maximal oxygen consumption, heart rate, and respiratory exchange ratio with the modified Bruce protocol. METHODS: We had five subjects (age 24 ±4) of two women and three males all from UTA. While subjects were tested on the LBPP treadmill their % body weight was at 70 and 100. Each subject performed a modified Bruce max test on the AlterG© treadmill. During each minute, absolute and relative maximal oxygen consumption (VO2max), heart rate (HR), and respiratory exchange ratio (RER) was measured by the CosmedK4b2 portable telemetric gas analysis system. After every stage, RPE was taken and then the time taken to maximal capacity. Each test was performed a week apart. RESULTS: The maximal values: HR (100%: 186 ±10.7 bpm; 70%: 185 ±12.0 bpm); RPE (100%: 16.8 ±1.1; 70%: 18.8 ±1.1); VO2max absolute (100%: 2.98 ±0.7 L/min; 70%: 3.01 ±0.8 L/min); VO2maxrelative (100%: 40.8 ±5.3 ml/kg/min; 70%: 40.6 ±6.1 ml/kg/min were not significantly different (p > 0.05). The average RER (100%: 1.04 ±0.05; 70%: 0.98 ±0.06) and the average time to get to max (100%: 13.6 ±3.1 minutes; 70%: 24.2 ±7.0 minutes) were statistically significant difference (p < 0.05). CONCLUSION: The study revealed that there was a no significant difference in the maximal values of heart rate, RPE, and absolute and relative VO2max on the AlterG© treadmills at different percentages of body weight. Removal of up to 30% bodyweight did not show to alter metabolic responses (VO2, HR, RER) during the modified Bruce protocol. Because the p-value was more than our alpha level of 0.05, the null hypothesis was accepted. Manipulation of body weight did not alter the contribution of the metabolically active muscle tissue required to maintain the forward velocity on the treadmill.