Pedometer-Assessed Ambulatory Activity and Cardiorespiratory Fitness

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. PURPOSE: 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). METHODS: 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). RESULTS: 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. CONCLUSION: 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.