Effects of long or short duration stimulus during high-intensity interval training on physical performance, energy intake, and body composition.

To compare the effects of 6 weeks of long or short high-intensity interval training (long- or short-HIIT) on body composition, hunger perception, food intake and rating of perceived exertion (RPE). Twenty previously untrained women (25±5 years) were randomly assigned to do a long-HIIT (n=10) or a short-HIIT (n=10). The long-HIIT group performed fifteen 1-min bouts at 90% of maximum heart rate (HRmax), interspersed by 30-sec active recovery (60% HRmax). The short-HIIT group performed forty-five 20-sec bouts at 90% of HRmax, interspersed by 10-sec active recovery (60% HRmax). The training for both groups was conducted 3 times a week for 6 weeks. All subjects performed the Astrand cycle ergometer test to estimate maximal oxygen consumption (VO) 1 week before and after the training period, as well as body composition, which was estimated through circumferences and skinfold thicknesses. For all training sessions, the heart rate, visual scale of hunger, internal load, and RPE were recorded. In the first and last week of training, subjects were asked to record a 24-hr food diary for 3 days. Both training induced significant pre to post decreases for fat mass, fat percentage, waist circumference, sum of seven skinfolds and RPE. As expected estimated, the VO increased in both groups. There were no differences for hunger perception, energy intake, and body mass. Long and short-HIIT resulted in fat loss, without altering the energy intake.