Standing or Very Low-Intensity Cycling as Sedentary Breaks: Does Physical Activity Level Matter?

Background: Active breaks and very low- to low-intensity exercises such as walking or cycling at an active desk have been shown to significantly counteract the negative effect of prolonged sedentary behaviors. The objective was to investigate the effect of physical activity level (PAL) on changes in energy expenditure (EE), heart rate, and substrate oxidation from sit-to-stand and sit-to-light cycling. Methods: Fifty healthy young males and females (age: 23.9 [3.9] y, body mass index: 22.9 [2.3] kg/m2) were submitted to a fixed 1 hour session of different posture allocations: 15-minute sitting, 15-minute standing, 15-minute sitting, and 15-minute very low-intensity cycling. EE, substrate oxidation rates, and heart rate were continuously assessed throughout the experimental visit. Data were then compared between participants according to their PAL in tertiles (low, medium, or high). The high-PAL group showed lower sedentary time (P < .0001) and higher time spent in low (P < .0001), moderate (P < .0001), and vigorous physical activity (P = .0034). Results: ANOVA's analysis showed that EE significantly increased when standing (+11%) and cycling (+94%) relative to the seated position (P < .05) without any differences between groups. There was also a significant increase in heart rate during standing and cycling compared with sitting (P < .05) without any differences between groups. Relative EE (in kilocalories per minute per kilogram) was significantly higher when seated (P < .05) independent of PAL but marginally higher in the high-PAL group when standing relative to the medium-PAL group (P = .06). Conclusion: The findings of this study suggest that people's PAL does not impact energetic and metabolic adaptations during sit-to-stand and sitto-very-light-intensity cycling exercise.