Background: Previous studies have suggested reduced fat metabolism in older subjects. However, corrections for their reduced maximal oxygen consumption and the effects of training and substrate availability have not been fully examined. Objectives: Fat metabolism (FM) in older subjects (n=14, 75±7 yrs), and the effects of exercise training were compared with FM in younger subjects (n=16, 22±3 yrs).Materials and Methods: All subjects completed a maximal exercise test and a sustained submaximal run at 70% of their maximal capacity. The Respiratory Exchange Ratio (RER) and blood substrate levels were determined. Older subjects were re-tested after training. Results: Young subjects had higher oxygen consumption (VO2) peak (36.3±6.7 vs. 23.7±6.2 ml/kg/min) and lower slope of RER vs. VO2 than older subjects. However, the slope of the RER vs. VO2 relationship was not different between younger and older subjects, after correction for their VO2 peaks. Younger subjects had longer sustained exercise times (45.5±17.6 min) than the elderly (30.2±14.0 min), pre-training. Post training, there was a significant increase in VO2 peak (25%) in older subjects (P=0.001) and submaximal exercise time (30.2±14.0 vs. 58.3±27.3min, P=0.020). Respiratory Exchange Ratio was reduced during both exercises after training (0.90±0.03 vs. 1.00±0.03, P=0.04). Conclusions: The RER of older subjects was not different from that of younger subjects, after correction for the VO2 peak. The VO2 peak, sustained exercise time, and RER decreased after training in older subjects, indicating increased fat metabolism.

Background: Studies reported conflicting results about the relationship between anthropometric factors, Respiratory Exchange Ratio, energy expenditure and VO2 max. Therefore the aim of this study was to investigate the relationship between anthropometric factors, Respiratory Exchange Ratio and energy expenditure with VO2 max in sedentary men.Materials and Methods: Thirty one sedentary healthy men (23.67±2.45 years old age, BMI=22.49±1.58 kg/m2) volunteered for participation this study. After the measurement of anthropometric factors, subjects performed an acute endurance exercise on the ergometer for determination of VO2 max. Subjects performed major protocol, one hour cycling on ergometer via 70% VO2 max for the determination of the Respiratory Exchange Ratio and the rate of energy expenditure, 72 hours later.Results: The results of this study showed that there is not any significant relationship between VO2 max and anthropometric factors, Respiratory Exchange Ratio and energy expenditure. Also, regression analysis indicated that all these variables cannot predicate the VO2 max.Conclusion: According to the results of this study anthropometric factors, Respiratory Exchange Ratio and energy expenditure are not strong predictors of VO2 max in sedentary young men.

Introduction: Respiratory Exchange Ratio (RER) is the Ratio between produced CO2 and used O2 for body metabolism. It indicates the type of fuel that is metabolized in the body. This study aimed to measure and compare the RER in non-obese and obese sedentary young adults in rest, moderate-intensity, and vigorous-intensity exercise. Methods: This cross-sectional study was conducted with 23 non-obese and 24 obese sedentary young adults. Resting RER was measured with 12-h fasting after 15-min rest with an automated gas analyzer. Then, RER was measured during steady moderate-intensity and vigorous-intensity exercise on a cycle ergometer. RER was compared between males and females, non-obese and obese in resting, moderate-intensity, and vigorous-intensity exercise by t-test. Results: The Mean age of the non-obese and obese groups was 19. 35±, 1. 11 and 19. 79±, 0. 78 years, respectively. Males showed higher RER (in resting and moderate-intensity exercise) than females. In comparison to non-obese group, the obese group showed higher RER in resting (0. 802±, 0. 018 versus 0. 821±, 0. 022, P=0. 001), moderate-intensity exercise (0. 812±, 0. 013 versus 0. 83±, 0. 02, P<0. 001), and vigorous-intensity exercise (0. 853±, 0. 43 versus 0. 914±, 0. 032, P<0. 001). Concerning resting value, RER significantly increased during moderate-and vigorous-intensity exercise in both the non-obese and obese groups. Conclusion: Obese young adults use relatively more carbohydrates as fuel than non-obese in both resting conditions and during exercise. When the intensity of exercise increased, both obese and non-obese showed higher RER which indicates that sedentary young adults use relatively more carbohydrates as fuel in the higher grade of exercise.

Background :Overweight and obesity have become a problem for younger geneRations, so weight management must be introduced. Moderate-intensity interval training (MIIT) has been recommended for aging and obese populations because it is friendly and accessible. However, little information is known about the physiological response during moderate-interval intensity exercise, especially for overweight and obese persons. Objectives :To evaluate cardioRespiratory alteRation upon a single bout of MIIT exercise among sedentary, overweight young Thai adults. Methods :Fifteen overweight young adults (8 males and 7 females, body mass index between 25.0 - 29.9 kg/m2, aged between 18 - 25 years) underwent cycling ergometry for 45 minutes (warm-up 5 minutes; 3 × 5 minutes at 20 - 40% of heart rate reserve and 5 minutes at 50 - 60%; cool down 10 minutes). A gas analyzer and limb lead electrocardiogram were used to record oxygen consumption (V̇O2), heart rate (HR), and dioxide production (V̇CO2) throughout the experiment. Results :During the 45-minute MIIT exercise protocol, the participants consumed 25.1 ± 8.1 L, equal to approximately 530 ± 171 kJ. As expected, heart rate, O2 uptake, and CO2 production increased during moderated-intensity exercise and declined during low-intensity exercise. A low to moderate duRation Ratio of 1: 1 was sufficient to return both O2 consumption and CO2 production to their stage level, but not for heart rate. Although there was a very linear relationship between V̇O2 and heart rate for the overall period (0.761 ± 0.090), the correlation was weaker when selectively computed during low (0.549 ± 0.161) or moderate exercises (0.658 ± 0.105). Interestingly, RER larger than one during moderate-intensity exercise indicated the possibility of high acid accumulation. Conclusions :The MIIT protocol in the present study provided a responsive effect on overweight persons toward anaerobic metabolism but was a little aggressive.