Does a variation in self-reported physical activity reflect variation in objectively measured physical activity, resting heart rate, and physical fitness? Results from the Tromso study

AIMS: To study the association between self-reported physical activity (PA) and objectively measured PA, resting heart rate, and physical fitness. METHODS: During 2007-08, 5017 men and 5607 women aged 30-69 years attended the sixth survey of the Tromsø study. Self-reported PA during leisure-time and work were assessed and resting heart rate was measured. In a sub-study, the activity study, PA (Actigraph LLC) and physical fitness (VO₂(max)) were objectively measured among 313 healthy men and women aged 40-44 years. RESULTS: Self-reported leisure PA was significantly correlated with VO₂(max) (ml/kg/min) (women 0.40, p <0.001, men 0.44 p <0.001) and moderate-to-vigorous PA (>2000 counts/min) (women 0.28, p <0.01, men 0.25, p <0.01). The intra-class correlation coefficient between self-reported leisure PA and overall PA (counts/min) measured by accelerometer was 0.62 (95% CI 0.51, 0.71) for women and 0.59 (95% CI 0.47, 0.69) for men, and for VO₂(max) the intra-class correlation coefficient was 0.86 (95% CI 0.81, 0.90) for both sexes. Among all participants, an inverse dose-response relationship was observed between self-reported leisure PA and resting heart rate for both men and women (p <0.0001). More women than men met the international recommendations of 10,000 step counts/day (27% vs. 22%) and the recommendation of at least 30 minutes/day of moderate-to-vigorous intensities (30% vs. 22 %). CONCLUSIONS: The Tromsø physical activity questionnaire has acceptable validity and provides valid estimates of high-intensity leisure activity. However, these results underscore the need for collecting objectively PA measurements in large epidemiological studies.