1475 The tracking of indicators of physical activity and submaximal exercise capacity from early adolescence to adulthood was examined in 164 participants from the Québec Family Study who were initially measured between 1979-1982 between the ages of 9-20 yrs, and again between 1989-1997 (average of 12 years follow-up). Indicators of physical activity included estimated daily energy expenditure (EE), and time spent in inactive (IA) and moderate-to-vigorous physical activities (MVPA). Physical work capacity at a heart rate of 150 beats min−1 (PWC150) was measured using a progressive exercise test on a cycle ergometer. All variables were adjusted for the effects of age using regression procedures, while PWC150 and EE were further adjusted for the effects of body mass, within sex. Tracking was assessed with inter-age Spearman rank order correlations between measurements in 1980 and 1992. Inter-age correlations are low to moderate over 12 years: 0.24 (p=0.03), 0.14 (NS), 0.27(p=0.02), and 0.14 (NS) in males and 0.50 (p<0.0001), 0.24 (p=0.04), 0.06 (NS), and 0.21 (NS) in females for PWC150, EE, MVPA, and IA, respectively. Associations among changes in indicators of activity and changes in PWC150 over 12 years were also examined. Change scores (deltas) were adjusted for the length of follow-up and baseline status using regression procedures. The correlations are low and not significant, indicating that changes in activity and inactivity over 12 years are not strongly associated with changes in submaximal exercise capacity. The results are consistent with observations that relationships among activity and fitness in youth are complex, and that tracking of physical activity and fitness from early adolescence into adulthood reaches only moderate levels. This research was supported by The Polar Research Grant on Controlled Heart Rate Zone Exercise from the American College of Sports Medicine Foundation.
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