Recommended Levels and Intensities of Physical Activity to Avoid Low-Cardiorespiratory Fitness in European Adolescents: The HELENA Study

Objectives: The purpose of this study was to determine the sex-specific physical activity (PA) intensity thresholds that best discriminate between unhealthy/healthy cardiorespiratory fitness (CRF). Methods: Participants included 1,808 adolescents (964 girls), aged 12.5-17.5 years, from the HELENA study. We measured PA by accelerometer and calculated the time spent at light, moderate, vigorous, and moderate-to-vigorous (MVPA) intensities. CRF was assessed by the 20-m shuttle-run test. Adolescents were dichotomized (unhealthy/healthy) based on sex- and age-specific FITNESSGRAM standards. Receiver operating characteristic (ROC) analysis was used to determine thresholds that best discriminate between CRF categories. Results: ROC analyses revealed that the PA thresholds that best discriminate between unhealthy/healthy CRF were >= 152, >= 33, >= 13, and >= 52 min/day in light, moderate, vigorous, and MVPA, respectively. In boys, the PA thresholds associated with a healthy CRF were >= 37, >= 19, and >= 56 min/day in moderate, vigorous, and MVPA, respectively, whereas in girls were >= 152, >= 34, >= 12, and >= 51 min/day in light, moderate, vigorous, and MVPA, respectively. Spending at least 60 min/day in MVPA was also associated with a healthy CRF (odds ratios: 1.75, 1.94, and 1.57, all P < 0.05, for the whole sample, boys, and girls, respectively). Conclusions: This study shows sex- and intensity-specific PA thresholds to discriminate between adolescents with a healthy CRF from those with a less favorable or unhealthy CRF level. Journal of Hospital Medicine. Society of Hospital Medicine. Am. J. Hum. Biol. 22:750-756, 2010. (C) 2010 Wiley-Liss, Inc.