Abstract:
The purpose of this study was to compare the acute and chronic effects of interval training on physiological responses, energy expenditure, vascular function, and physical fitness in participants with morbid obesity. In the acute exercise study, 12 lean (BMI 18.5-22.9 kg/m2) and 12 obese (BMI ≥37.5 kg/m2) males and females, aged 18-50 years, performed an acute bout of continuous training and interval training. The physiological variables, vascular function, energy expenditure and enjoyment score were measured before and after the acute exercise. A 2x3 ANOVA with repeated measures was applied to analyze the data followed by LSDs multiple comparisons. The results from study 1 were used to set exercise intensity in the chronic exercise study. In the chronic exercise study, twenty-six males and females were divided into 2 groups based on their BMI: lean group, BMI 18.5-22.9 kg/m2 (n=26) and obese group with BMI ≥37.5 kg/m2 (n=12). Both groups performed high-intensity interval training 5 times per week for 12 weeks. In the first 1-6 weeks, the training comprised of six sets alternating between high intensity (1 minute at 75-85% HRR) and low intensity (4 minutes at 45-55% HRR). In the 7-12 week, participants performed exercise at intensity-level as session 1 but add 2 more sets (8 sets). Every training started with 10-minute warm-up, and ended with 15-minute cool-down. Body composition, vascular function, physical fitness, blood biochemical data, and quality of life were measured before and after the 12-week trainings. A 2x3 ANOVA with repeated measurement was applied to analyze the data followed by LSDs multiple comparisons. The results of the study were as follows: In the acute exercise study, obese participants had higher energy expenditure than lean participants during both continuous training and interval training (p<0.05). The enjoyment score was significantly higher in high intensity interval training than in continuous training (p<0.05), and flow-mediate dilation was increased in both groups (p<0.05). In the chronic exercise study, the obese group increased muscle mass and bone mass density after the training (p<0.05). Flow-mediated dilation, an index of endothelium dependent vasodilation was increased, but intima-media thickness decreased in the obese group (all p<0.05). The obese group had higher muscle strength than the lean group. Muscle endurance (1 minute sit to stand test) and flexibility, maximal oxygen uptake were all increased in the lean group (all p<0.05). Resting metabolic rate and fat oxidation were reduced in the obese group (all p<0.05). Low density lipoprotein cholesterol decreased in the obese group (p<0.05). Plasma concentration of Leptin decreased but adiponectin and high-density lipoprotein cholesterol were increased in the lean group (all p<0.05). Quality of life scores in obese participants were significantly lower than lean participants (p<0.05) In conclusion, interval training can be a feasible and effective exercise for enhancing body composition vascular function and muscle strength and endurance in morbidly obese adults. The interval training is safe, noninducing injury and enjoyable training.