Effects of single bout of very high-intensity exercise on metabolic health biomarkers in overweight/obese sedentary men

Purpose: 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. <p/>Methods: Ten overweight/obese men aged 26.9 ± 6.2 years participated. Following a pre-trial incremental exercise test and SIT familiarization, each participant undertook three 2-day trials in randomized order. On Day 1 participants either undertook no exercise (CON), four maximal 30-s sprints, with 4.5 min recovery between each (SIT), or a single maximal extended sprint (ES) matched with SIT for work done. On Day 2, participants had a fasting blood sample taken, undertook an oral glucose tolerance test to determine insulin sensitivity index (ISI), and had blood pressure measured. <p/>Results: Total work done during exercise did not differ between SIT and ES (61.7 ± 2.9 vs. 61.3 ± 2.8 kJ; p = 0.741). Mean power was higher in SIT than ES (518 ± 21 vs. 306 ± 16 W, p < 0.0005), resulting in a shorter high-intensity exercise duration in SIT (120 ± 0 vs. 198 ± 10 s, p < 0.0005). ISI was 44.6% higher following ES than CON (9.4 ± 2.1 vs. 6.5 ± 1.3; p = 0.022), but did not differ significantly between SIT and CON (6.6 ± 0.9 vs. 6.5 ± 1.3; p = 0.208). 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 (p < 0.05 for both), with a concomitant reduction in carbohydrate oxidation (p < 0.05). <p/>Conclusion: A single ES, which may represent a more time-efficient alternative to SIT, can increase insulin sensitivity and increase fat oxidation in overweight overweight/obese sedentary men