Metabolic Effects of Reduced Volume Sprint Interval Training During and Postexercise

McCarthy, SF, McKie, GL, Howe, GJ, Vanderheyden, LW, and Hazell, TJ. Metabolic effects of reduced volume sprint interval training during and postexercise. J Strength Cond Res 38(5): 891-897, 2024-It is unclear what dose of sprint-interval training exercise (exercise volume) is required to derive beneficial metabolic effects during and postexercise. Therefore, we examined how reducing the volume of sprint interval training (SIT) from 2 minutes of "all-out" efforts (8 bouts) to 1.5 minutes (6 bouts) and 1 minute (4 bouts) affected during and postexercise metabolism. Fourteen recreationally active males (age: 25 +/- 3 years; body mass index: 25.1 +/- 3.1 kg<middle dot>m(-2)) had gas exchange measured during and following (3 h) 4 experimental sessions: (a) no-exercise control (CTRL), (b) 8 x 15 SIT (2 minutes exercise), (c) 6 x 15 minutes SIT (1.5 minutes exercise), and (d) 4 x 15 SIT (1 minute exercise). All SIT protocols were 15 seconds "all-out" running efforts with 2 minutes recovery (4, 6, or 8 bouts). Changes were considered important if p < 0.100 and the effect size was >= medium. During exercise, oxygen consumption (Vo(2); L) was different between protocols (p < 0.001, d > 2.98) and greater than CTRL (p < 0.001, d > 2.12); however, the rate of o(2) consumption (L<middle dot>min-1) was similar between protocols (p = 0.479, eta(2)(p) = 0.055). Total Vo(2) (L) postexercise was elevated following all conditions compared with CTRL (p < 0.003, d > 1.25). Overall session Vo(2) was different in each condition (p < 0.001, d > 1.89). Fat oxidation was elevated postexercise following all SIT protocols compared with CTRL (p < 0.017, d > 0.98) with no differences between protocols (p > 0.566, d < 0.48). Our results suggest reducing the number of all-out 15 seconds bouts during a SIT session from 8 to 6 or 4 had no differential effects on postexercise metabolism and differences during exercise were due to the longer duration of exercise.