Effects of reducing sedentary behaviour on cardiovascular health, skeletal muscle oxidative capacity and functional exercise capacity in sedentary adults: a randomised controlled trial.

Purpose: This study aimed to investigate the effectiveness of a 12-week intervention using self-monitoring alone and in combination with motivational interviewing to reduce sedentary behaviour (SB) and improve cardiovascular health, as reflected by cardiac autonomic function, endothelial function, skeletal muscle oxidative capacity and functional exercise capacity in sedentary adults. Methods: In a three-armed randomised controlled trial, 59 (36% male; age: 53.3±8.7 years) sedentary adults were randomly allocated to a control group, a self-monitoring (consumer wearable activity tracker, CWAT) group or the self-monitoring+motivational (CWAT+) group for 12 weeks. SB and physical activity were assessed using activPAL3 accelerometer. Endothelial function was assessed using non-invasive peripheral arterial tonometry with the EndoPAT2000 device and fasting blood samples. Muscle oxidative capacity was evaluated using a submaximal cardiopulmonary exercise test, functional exercise capacity via a 6 min walk test, and cardiac autonomic function through heart-rate variability analysis. Results: The CWAT+group significantly reduced time spent in SB, which resulted in improvements in muscle oxidative capacity (time constant τ: -4.9 s±10.9 s; p=0.010), functional exercise capacity (6 min walking distance: +53 m±36 m; p=0.014) and measurements of heart rate variability (HRV) reflected by the root mean square of successive differences between normal adjacent R-R intervals (112 23 ms; p=0.014), low-frequency component (1178 (11, 2344) ms Conclusion: A reduction in SB results in improvements of HRV, skeletal muscle oxidative capacity and functional exercise capacity in sedentary adults, mainly driven by an increase in moderate-to-vigorous physical activity. Trial registration number: NCT03853018.