Relative importance of step count,intensity,and duration on physical activity's impact on vascular structure and function in previously sedentary older adults

Background: age-related endothelial dysfunction and vascular stiffening are associated with increased cardiovascular (cv) risk. many groups have encouraged goals of ≥10 000 steps/day or ≥30 min/day of moderate intensity physical activity (mpa) to reduce age-related cv risk. the impact of mpa on the vasculature of older adults remains unclear. methods and results: we randomized 114 sedentary older adults ages ≥50 to 12 weeks of either no intervention (group 1),a pedometer-only intervention (group 2),or a pedometer with an interactive website employing strategies to increase the adoption of habitual physical activity (pa,group 3). endothelial function by brachial flow-mediated dilation (fmd%),vascular stiffness by tonometry,step-count by pedometer,and pa intensity/distribution by accelerometer were measured. step-count increased in groups 2 (5136±1554 to 9596±3907,p<0.001) and 3 (5474±1512 to 8167±3111,p<0.001) but not in group 1 (4931±1667 to 5410±2410). both groups 2 and 3 increased mpa ≥30 min/day. only group 3 increased mpa in continuous bouts of =10 minutes (p<0.001) and improved fmd% (p=0.001). neither achievement of ≥10 000 steps/day nor ≥30 min/day of mpa resulted in improved fmd%. however,achieving ≥20 min/day in mpa bouts resulted in improved fmd%. no changes in vascular stiffness were observed. conclusions: mpa reverses age-related endothelial dysfunction,but may require mpa to be performed in bouts of ≥10 minutes duration for ≥20 min/day to be effective. commonly encouraged pa goals do not guarantee improved endothelial function and may not be as effective in reducing cv risk. © 2014 by american heart association,inc.