F18l Free Communication/Poster Epidemiology and Preventive Medicine
Low cardiorespiratory fitness and physical inactivity likely have related health consequences. Conclusions about the associations between free-living physical activity (PA) and enhanced fitness, however, are limited to previous use of questionnaire data to assess daily PA.
To examine the relationship between an objective method to assess lifestyle PA (pedometer-determined ambulatory activity in steps/day) and cardiorespiratory fitness indicators (submaximal exercise heart rate or HR and blood pressure or BP).
Data were obtained from 98 subjects (7 African American males, 16 African American females, 33 Caucasian males, and 42 Caucasian females; mean age = 46.4 ± 15.4; mean BMI = 26.7 ± 4.8) who wore a pedometer for 21 consecutive days and completed a 10 min submaximal treadmill graded exercise test with HR (beats/min) and BP (mmHg) measured while walking at 4.8km/hour and a 10% grade. Analyses were stratified by self-reported participation in vigorous PA (yes vs. no).
Subjects averaged 7,618 ± 3,045 steps/day. There were no differences in steps/day for subjects stratified by vigorous PA participation. There was an inverse relationship (r = 0.35, p = 0.03) between steps/day and HR response at rest in subjects reporting no participation in vigorous PA. There was an inverse relationship (r = −0.22, p = 0.04) between steps/day and submaximal HR exercise in all subjects. When stratified for self-reported participation in vigorous PA, the inverse relationship between steps/day and submaximal HR was stronger for those reporting no vigorous PA (r = −0.39, p = 0.01) vs. those reporting any vigorous PA (r = −0.28, p = 0.05). There was no relationship between steps/day and BP at rest or during exercise in this normotensive sample.
Increased pedometer-assessed steps/day are related to a lower HR response to acute submaximal exercise reflecting the influence of daily PA on fitness measures. The magnitude of the relationship varies with self-reported participation in vigorous PA. Supported by the USC Prevention Research Center.