Physical Activity Intensity and Cardiometabolic Risk in Youth.

OBJECTIVE To determine the association between physical activity (PA) intensities and cardiometabolic risk factors in youth. DESIGN Cross-sectional study using data from the 2008 Healthy Hearts Prospective Cohort Study of Physical Activity and Cardiometabolic Health in Youth. SETTING Rural and urban communities in Alberta, Canada. PARTICIPANTS A convenience sample of 605 youth aged 9 to 17 years. Youth were on average aged 12.1 years, 248 were boys (41%), and 157 were overweight or obese (26%). MAIN EXPOSURE Actical accelerometer-measured PA intensity. MAIN OUTCOMES MEASURES The primary outcome was body mass index (calculated as weight in kilograms divided by height in meters squared) z score. Secondary outcome measures included waist circumference, systolic blood pressure, and cardiorespiratory fitness (maximal oxygen consumption [[Vdot]O2max]). RESULTS Body mass index z score, waist circumference, and systolic blood pressure decreased and [Vdot]O2max increased in a dose-response manner across tertiles of vigorous PA (adjusted P < .001). No significant differences in cardiometabolic risk factors were seen across tertiles of moderate or light PA in multivariable analyses. Achieving more than 7 minutes of vigorous PA daily was associated with a reduced adjusted odds ratio of overweight status (0.56; 95% CI, 0.33-0.95) and elevated systolic blood pressure (0.36; 95% CI, 0.16-0.79). The odds of overweight status and elevated blood pressure decreased with increasing time and intensity of PA. CONCLUSIONS Only vigorous PA was consistently associated with lower levels of waist circumference, body mass index z score, systolic blood pressure, and increased cardiorespiratory fitness in youth. These findings underscore the importance of vigorous PA in guidelines for children and adolescents.