Effects of reducing sedentary behaviour on heart rate variability and cardio‐metabolic biomarkers in desk workers with untreated high blood pressure

Lower sedentary behaviour (SB) has been associated with reduced cardiovascular disease and mortality. Yet, few trials have evaluated cardiovascular mechanisms of benefit. We examined the effects of a SB reduction intervention on heart rate variability (HRV) and cardio-metabolic biomarkers. We evaluated secondary outcomes in RESET-BP, a randomized clinical trial testing the effects of a 3-month SB reduction intervention on blood pressure (BP) in desk workers with untreated high BP. The intervention included health coaching, sit-stand desks, wearable activity prompters and text messages that reduced SB by increasing standing (∼1 h/day) and stepping (∼5 min/day). Resting HRV was assessed in a subset of participants. Fasting blood plasma and serum were drawn to evaluate several cardio-metabolic biomarkers, including glucose, insulin, lipids, aldosterone and plasma renin activity. Analysis of covariance models examined the effect of the intervention on outcomes. Participants with baseline and follow-up measures of HRV (n = 146) and cardio-metabolic biomarkers (n = 188) were included. No significant intervention effects were observed for any measures of HRV, glucose, insulin or lipids (all P > 0.05). Three-month changes in aldosterone (difference = -1.5 ng/dL; P = 0.0370) and plasma renin activity (difference = -0.2 ng/mL/h; P = 0.0462) were significantly lower in the intervention compared to the control condition at the 3-month follow-up. Reducing SB with mostly standing did not improve HRV or cardio-metabolic biomarkers. However, the observed intervention effects on plasma renin and aldosterone encourage future research to confirm that SB reduction suppresses the renin-angiotensin-aldosterone system activity.