Short Sprints Good for Fat Oxidation

High-intensity interval training is one of the hottest types of training these days. Several studies have examined its long-term effects. Recently, researchers wanted to learn about the impact of a single short bout of HIIT.

The small study, published in Metabolism—Clinical and Experimental (2013; 62 [2], 212–19), included 10 overweight and obese men, aged approximately 26 years. “This study aimed to investigate the effects of a single session of sprint interval training (SIT) and a single extended sprint (ES), matched for total work, on metabolic health biomarkers,” explained the authors.

During one session, subjects participated in one of three protocols: SIT, ES or no exercise (control condition, CON). The SIT group performed four maximal 30-second sprints, with 4.5 minutes’ rest between them. The ES group performed one maximal sprint, achieving the same amount of work done as the SIT group. The next day, the scientists took fasting blood samples, measured blood pressure, and determined subjects’ insulin
sensitivity indices by testing their oral glucose tolerance.

Based on the data, the authors concluded that “a single ES, which may represent a more time-efficient alternative to SIT, can increase insulin sensitivity and increase fat oxidation in overweight/obese sedentary men.” Nonetheless, fat oxidation was higher in the SIT group.

“[Insulin sensitivity index] was 44.6% higher following ES than CON, but did not differ significantly between SIT and CON,” the authors explained. “However, on the day following exercise, fat oxidation in the fasted state was increased by 63% and 38%, compared to CON, in SIT and ES, respectively, with a concomitant reduction in carbohydrate
oxidation.”