Abstract
The effects of two high-intensity interval training (HIIT) protocols on regional body composition and fat oxidation in men with obesity were compared using a parallel randomized design. Sixteen inactive males (age, 38.9 ± 7.3 years; body fat, 31.8 ± 3.9%; peak oxygen uptake, VO2peak, 30.9 ± 4.1 mL/kg/min; all mean ± SD) were randomly assigned to either HIIT10 (48 × 10 s bouts at 100% of peak power [Wpeak] with 15 s of recovery) or HIIT60 group (8 × 60 s bouts at 100% Wpeak with 90 s of recovery), and subsequently completed eight weeks of training, while maintaining the same diet. Analyses of variance (ANOVA) showed only a main effect of time (p < 0.01) and no group or interaction effects (p > 0.05) in the examined parameters. Total and trunk fat mass decreased by 1.81 kg (90%CI: −2.63 to −0.99 kg; p = 0.002) and 1.45 kg (90%CI: −1.95 to −0.94 kg; p < 0.001), respectively, while leg lean mass increased by 0.86 kg (90%CI: 0.63 to 1.08 kg; p < 0.001), following both HIIT protocols. HIIT increased peak fat oxidation (PFO) (from 0.20 ± 0.05 to 0.33 ± 0.08 g/min, p = 0.001), as well as fat oxidation over a wide range of submaximal exercise intensities, and shifted PFO to higher intensity (from 33.6 ± 4.6 to 37.6 ± 6.7% VO2peak, p = 0.039). HIIT, irrespective of protocol, improved VO2peak by 20.0 ± 7.2% (p < 0.001), while blood lactate at various submaximal intensities decreased by 20.6% (p = 0.001). In conclusion, both HIIT protocols were equally effective in improving regional body composition and fat oxidation during exercise in obese men.
Highlights
During the last four decades, there has been a dramatic increase in the prevalence of obesity worldwide [1] with trends indicating a further rise until 2030 [2]
Obesity is a disease associated with increased premature morbidity and mortality, which is partially explained by a disturbed energy balance characterized by overfeeding, reduced physical activity and impaired fat oxidation [3]
Bold font highlights statistically significant differences. 90% CI, 90% confidence interval; η2, partial eta squared; ES, effect size; COP, crossover point; PCHO, peak carbohydrate oxidation rate; Fatpeak, exercise intensity corresponding to peak fat oxidation; HRpeak, peak heart body mass; PFO, peak fat oxidation rate; VO2peak, peak oxygen
Summary
During the last four decades, there has been a dramatic increase in the prevalence of obesity worldwide [1] with trends indicating a further rise until 2030 [2]. Obesity is a disease associated with increased premature morbidity and mortality, which is partially explained by a disturbed energy balance characterized by overfeeding, reduced physical activity and impaired fat oxidation [3]. Among the main barriers to physical activity are the reported lack of time and the inability to adhere to lengthy exercise programs [6]. Accumulating evidence suggests that HIIT can act as a “gateway to exercise”, helping individuals to initiate an exercise program, as it reduces the time commitment to exercise, while having positive effects on body composition and energy metabolism [7]
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