The effects of uninterrupted and interrupted sitting on blood pressure and arterial stiffness in patients with established coronary heart disease.

Sedentary behaviour is an independent risk factor for cardiovascular disease. In healthy adults, prolonged uninterrupted sitting acutely increases blood pressure (BP) and aortic stiffness; however, these effects can be mitigated with light physical activity interruptions. Whether such mitigation strategies are effective in at-risk populations remains unclear. This study examined the effects of uninterrupted and interrupted sitting on BP and arterial stiffness, measured by carotid-femoral pulse wave velocity (cfPWV), and femoral-ankle PWV in patients with established coronary heart disease (CHD). Using a randomised cross-over design, 14 CHD patients sat for 2 h uninterrupted (control [CON]), and 2 h interrupted with light physical activity (sit-to-stand, calf raises and walking) breaks every 30 min (ACT). Brachial BP and cfPWV were assessed immediately pre- and post-sitting. Time-by-condition effects were tested using linear mixed effects models with baseline adjustments. A significant time × condition interaction effect was detected for systolic BP (P = 0.037) with an increase in CON (mean difference [MD] = 15 mmHg [95% CI: 8, 23], P < 0.001) but not ACT (MD = 4 mmHg [95% CI: -4, 11], P = 0.334). A significant time effect was detected for cfPWV, with an increase across both CON and ACT conditions (MD = 0.76 m/s [95% CI: 0.52, 0.99], P < 0.001). For CHD patients, light activity breaks every 30 min can attenuate the impact of prolonged sitting on BP but not arterial stiffness; higher frequency or intensity of activity breaks may be required for better preservation of cardiovascular function.