Multiple Shorter High‐Intensity Interval Exercise Sessions During the Day Result in Greater Energy Expenditure With Less Exertion Than a Longer Single Session: A Randomized Crossover Clinical Trial

Breaking up periods of sedentary time with brief bouts of high-intensity interval exercise (HIIE) is suggested as a time-efficient approach to improve exercise adherence and health. This randomized crossover clinical trial was designed to compare energy expenditure (EE), cardiometabolic, and perceptual responses during HIIE performed in a single session (1xHIIE) or split into three shorter sessions (3xHIIE) throughout the day. Fifteen male participants (48.5 ± 2.9 years) completed two experimental protocols: 1xHIIE protocol consisted of a single 21 min session, whereas the 3xHIIE protocol consisted of three shorter 7 min sessions separated by a 4 h interval between each session. Oxygen consumption (VO₂), heart rate (HR), rate of perceived exertion (RPE), and blood lactate were measured during the experimental protocols. The 1xHIIE and 3x HIIE sessions induced similar EE (298.20 ± 51.74 and 299.32 ± 69.18 kcal, respectively; p = 0.88). However, postexercise EE following the 3xHIIE was approximately twice as high as the 1xHIIE (62.97 ± 14.97 vs. 27.42 ± 8.98 kcal, respectively; p < 0.001) or approximately 36 kcal higher. Additionally, compared to 1xHIIE, the 3x HIIE protocol induced lower HR (158 ± 12 and 147 ± 8 bpm, respectively; p = 0.018), rating perceived effort (15.8 ± 1.8 and 14.4 ± 1.7 respectively; p = 0.0012), and blood lactate (7.7 ± 3.7 and 5.4 ± 1.8 mmol/L, respectively; p = 0.013). These findings suggest that multiple brief sessions of HIIE throughout the day result in a greater energy expenditure with less perceived exertion than a single HIIE session in middle-aged male individuals.