A lack of physical activity plays an important role in cardiovascular disease, however the mechanism(s) are poorly understood. In addition, the majority of studies which have examined the relationship between physical activity and arterial function have used subjective measures of activity. The aim of this cross-sectional study was to investigate if objectively measured physical activity is associated with arterial stiffness and wave reflection in patients attending an outpatient hypertension clinic.
Design and Method:
Physical activity was measured for 7 consecutive days using a triaxial accelerometer (RT3 Stayhealthy). This provides data on estimated energy expenditure in physical activity and time spent in the various intensities of activity. Brachial blood pressure (BP) was measured using an oscillometric technique (Omron) in the right arm. Using the same arm, augmentation index (AIx) and aortic BP were measured using radial applanation tonometry (SphygmoCor). Pulse wave velocity (PWV) was measured using the foot-to-foot method (Artech Medical).
Eighty adults (female, n = 40) with a mean ± sd age 49 ± 25y, body mass index (BMI) 29.7 ± 5.1 kg/m2 (n = 70) and waist circumference 101 ± 14 cm (n = 42) participated. PWV was 10.3 ± 2.4m/s (n = 36) and AIx was 27.1 ± 14.4% (n = 48). Physical activity data was available for n=53 patients. Time spent in at least moderate physical activity was 36 ± 31 minutes/d and n = 26 (49%) patients carried out at least 30 minutes/d of at least moderate intensity activity. AIx and aortic BP were significantly lower in those who engaged in higher amounts of vigorous activity (P < 0.01)(n = 48). In stepwise regression analysis, after adjusting for age, gender, BMI, alcohol intake and smoking, the only independent predictors of AIx were physical activity, heart rate and systolic BP. There was no relationship between physical activity and PWV (n = 36).
Physical activity reduces aortic wave reflections and BP, independent of BP and age probably because of increased nitric oxide production in the medium sized arteries. This reiterates the importance of regular physical activity in hypertensive patients to maintain optimum wave reflections.