Sprint exercise snacking versus volume-matched intermittent-sprint exercise: acute metabolic and hormonal responses in overweight men

Background and Purpose: Exercise snacking has recently emerged as a novel, time-efficient, and practical strategy for improving metabolic health and cardiometabolic outcomes. This approach typically involves the distribution of very brief bouts of high-intensity exercise across the day, aiming to maximize metabolic stimulation while minimizing total time commitment. Although exercise snacking may improve glycemic control, aerobic fitness, and energy expenditure, human data comparing the effect of sprint-based exercise snacking and volume-matched intermittent-sprint exercise performed within a single session are scarce and we aimed to compare the acute metabolic and hormonal responses to these two exercise protocols in overweight men.
Materials and Methods: In this randomized crossover design study 14 overweight men completed a single session of intermittent-sprint exercise (ISE), and a volume-matched intermittent-sprint exercise performed separately in the morning and afternoon (SES1 + SES2). Each sprint bout was based on a Wingate-style protocol. Respiratory gas exchange was continuously measured to assess excess post-exercise oxygen consumption (EPOC), respiratory exchange ratio (RER), and fat and carbohydrate oxidation, both cumulatively and at discrete time points, throughout a 30-minute recovery period following exercise. Venous blood samples were obtained at baseline, immediately post-exercise, and 30 minutes into recovery to determine concentrations of lactate, glucose, insulin, cortisol, the cortisol-to-insulin ratio, epinephrine, norepinephrine, glycerol, and non-esterified fatty acids (NEFA).
Results: The findings demonstrated that the exercise snacking condition elicited significantly greater increases in EPOC, total energy expenditure, and cumulative oxidation of both fat and carbohydrate substrates compared to the volume-matched intermittent-sprint exercise condition (p<0.05). In contrast, glycolytic and sympathoadrenal responses, reflected by higher post-exercise lactate and catecholamine concentrations, were significantly higher immediately after the intermittent-sprint exercise session. Conversely, lipolytic markers, including circulating glycerol and NEFA concentrations, were significantly elevated during the late recovery phase following exercise snacking compared with intermittent-sprint exercise (p<0.05). No significant differences were observed between conditions for mean RER or point-specific substrate oxidation rates during the recovery period.
Conclusion: These findings indicate that distributing sprint exercise across the day in the form of exercise snacks, despite identical total exercise volume and intensity, induces greater cumulative metabolic stimulation and post-exercise energy expenditure than performing the same workload within a single intermittent session. This pattern appears to promote a more favorable lipolytic environment during recovery, which may have implications for enhancing fat oxidation in overweight men.