Abstract
Chronic sedentary behavior increases risk for cardiovascular disease, which is the leading cause of death globally. Sitting impairs leg vascular health. Simple perturbations to increase leg blood flow prevent impairments, however, the effects on central cardiovascular health are unknown. Arterial stiffness (AS) is an indicator of CVD, and Pulse Wave Velocity (PWV) is a non-invasive measure of arterial compliance. Pulse Wave Analysis (PWA) measures augmentation index (AIx) and central pressure provides additional information about AS.
PURPOSE: To investigate the effects of prolonged sitting, with and without calf raises on aortic AS (carotid-femoral PWV) central blood pressure (CBP), and AIx.
METHODS: After familiarization, sedentary participants (n=20, 21.7 yrs (2.9), BMI 25.7 m/kg2 (5.3), 70% female) sat for 180 minutes with and without performing 10 calf raises every 10 minutes in a random order. Following 20 min of supine rest, baseline vascular measures were collected. Measures of CBP and AIx were recorded at 10, 90, and 170 min of sitting. Near-infrared spectroscopy (NIRS) was used to assess total hemoglobin (tHB) concentration in the gastrocnemius muscle (index of blood pooling). Data were analyzed with a linear mixed model and are presented as mean difference (SE).
RESULTS: PWV increased significantly (0.30 m/s (0.46), p <0.001) while AIx significantly decreased (-9.2% (11.0), p<0.001). tHb tended to increase with sitting (0.9 (1.0), p=0.082) and in the control condition (2.1 (1.0), p=0.084).
CONCLUSIONS: Sitting increases aortic AS but decreases AIx, an effect which may be mediated by blood pooling in the lower leg. Intermittent calf raises are insufficient to alter AS, as PWV increased by 0.30 m/s acutely. Despite being below the clinical threshold of 1.0 m/s with chronic inactivity, the acute increases in PWV in 3 hours may increase heart burden and become meaningful over time.