The Impact of Moderate Intensity Physical Activity on Cardiac Structure and Performance in Older Sedentary Adults

BACKGROUND:Sedentary aging leads to adverse changes in vascular function and cardiac performance. We published improvements in vascular function with moderate intensity physical activity (PA) in continuous bouts. Whether moderate intensity PA also impacts cardiac structure and cardiovascular performance of the aging left ventricle (LV) is unknown.METHODS:We recruited and analyzed results from 102 sedentary older adults ages ≥ 50 from a randomized controlled trial with 3 study groups: control (group 1), a pedometer-only intervention (group 2), or a pedometer with an interactive website employing strategies to increase habitual physical activity (PA, group 3) for 12 weeks. Transthoracic echocardiograms were performed prior to and following the 12 week intervention period to assess cardiac morphology, left ventricular (LV) systolic performance, LV diastolic function, arterial and LV ventricular elastance. Step count and PA intensity/distribution were measured by pedometer and accelerometer.RESULTS:We found no significant changes in cardiac morphology. Further, we found no improvement in the aforementioned cardiac functional parameters. Comparing those who achieved the following benchmarks to those who did not showed no significant changes in cardiac structure or performance: 1)10,000 steps/day, 2) ≥ 30 minutes/day of moderate intensity physical activity, or 3) moderate intensity PA in bouts ≥ 10 minutes for ≥ 20 minutes/day.CONCLUSIONS:In sedentary older adults, increasing moderate intensity PA to currently recommend levels does not result in favorable changes in LV morphology or performance over 12 weeks. More prolonged exposure, higher PA intensity, or earlier initiation of PA may be necessary to see benefits.