Abstract 15178: Physical Activity Architecture and Endothelial Function in Older Adults: Importance of Activity in Bouts
Introduction: National recommendations for physical activity (PA) in adults ages ≥ 50 years include near daily moderate intensity PA (3-6 METs) of at least 30 minutes duration, approximated by an average step count of 10,000 steps/day. ¾ of older adults fail to reach this target. Limited direct evidence exists supporting that the recommended amount, intensity, and distribution of PA improves endothelial function, a key surrogate for cardiovascular risk.
Methods: We randomized 114 sedentary adults ages ≥ 50 years to one of three study arms: 1) control arm, 2) pedometer only arm with verbal instructions to achieve 10,000 steps/day, and 3) a pedometer with access to an interactive website designed with motivational messaging to encourage reaching the 10,000 steps/day goal by 12 weeks. The program teaches older adults to integrate moderate intensity PA into their daily lives in bouts of ≥10 minutes duration. Vascular endothelial function was measured by brachial artery flow mediated dilation (FMD%) prior to and at the end of a 12 week intervention period. Duration and intensity of PA were measured by accelerometry.
Results: 107 subjects completed the study (71% female, age 63±7, baseline steps 5150±1588). Average daily step count increased (P<0.001 for interaction) in groups 2 (5136±1553 to 9596±3907) and 3 (5474±1511 to 8168±3211) but not in group 1 (4931±1668 to 5410±2410). FMD% increased only in group 3 (5.2±2.6 to 8.0±4.4%, P=0.03) with no changes in groups 1 (5.6±2.5 to 6.3±2.7%) or 2 (6.5±3.0 to 6.7±3.4%). While both groups 2 and 3 primarily increased PA through moderate intensity activity, only group 3 significantly increased its PA in bouts ≥10 minutes. Subjects who averaged ≥ 20 minutes/day of moderate intensity activity in ≥10 minute bouts (N=33) at week 12 had improved FMD% (5.8±3.2 to 8.0±3.8, P=0.04). At week 12, averaging ≥30 minutes/day of moderate intensity PA or averaging 10,000 steps/day without meeting the ≥20 minute bout threshold failed to improve FMD%.
Conclusion: Increasing moderate intensity PA can improve endothelial function in older adults, but the structure of that activity is important to its cardiovascular impact. Further work is necessary to determine the optimal duration, intensity, and architecture of PA interventions in older adults.
- © 2013 by American Heart Association, Inc.