Effect of Postural Changes on Resting Metabolic Rate and Substrate Utilization
1Department of Exercise and Sport Sciences, Faculty of Sport Sciences, Hacettepe University, Ankara, Turkey
2Department of Recreation, Faculty of Sport Sciences, Hacettepe University, Ankara, Turkey
Keywords: Posture, resting metabolic rate, heart rate, minute ventilation, substrate oxidation
Objective: While supine position is the classical method to measure resting metabolic rate (RMR), the effects of postural changes on RMR is not clear. The aim of this study is to examine the effect of postural changes on RMR and substrate utilization.
Material and Methods: RMR was measured in 23 sedentary male subjects (age: 26.7±5.8 yr) after an overnight fast for 10 min in random order for supine, sitting and standing positions. An automated gas analysis system was used to measure oxygen consumption (VO2), carbon dioxide production (VCO2), minute ventilation (VE), and heart rate (HR) to determine RMR. RMR was calculated with Weir’s formula, whereas rates of carbohydrate (CHO) and free fatty acid (FFA) utilization were calculated with Frayn’s formula. One way ANOVA with Bonferroni post hoc test was used to calculate the effect of postural changes on variables, and one sample t-Test was used to identify the difference between resting VO2 and 1 MET levels.
Results: RMR values measured in supine and sitting positions were similar, both of which were significantly lower than those measured in the standing position (p<0.01). Both VE and HR values measured in all three positions were different (p<0.01). VO2 levels measured in supine and sitting positions were significantly lower than 1 MET (3.5 ml.kg-1. min-1) (p<0.01), while VO2 measured in standing position was similar with 1 MET (p>0.05). Rate of CHO utilizationwas similar in sitting and standing positions, whereas in the supine position, this rate was significantly higher than in the sitting position (p<0.01). Conversely, rate of FFA utilization was significantly different in all three positions (p<0.01). The lowest rate of FFA utilization was measured in the supine position, while the highest was measured in the standing position.
Conclusion: Findings of this study indicated that postural change significantly affected RMR and activity of the cardio-pulmonary system. In addition, substrate utilization has shifted from CHO to FFA in accordance with postural changes.
Cite this article as: Hazir T, Denizli G, Ulupinar S, et al. Effect of postural changes on resting metabolic rate and substrate utilization. Turk J Sports Med. 2018;53(4):142-51.