Cardiorespiratory fitness of males and females of northern Finland birth cohort of 1966 at age 31.

This study aimed to measure cardiorespiratory fitness of about 9000 males and females at age 31, to produce the reference values and relate them to the level of physical activity and body mass index (BMI). Study population was the Northern Finland birth cohort of 1966. At age 31, 8786 persons responded to a postal inquiry including questions about physical activity and 5497 of them also performed a step test. A sample of 123 persons performed a maximal exercise test with direct measurement of peak oxygen uptake (VO(2peak)). This was done to develop VO(2peak) prediction models on the basis of heart rate after a step test, BMI and frequency of brisk physical activity. These models were used to calculate VO(2peak) for the whole study population. Mean VO(2peak) +/- standard deviation was 43.0 +/- 4.6 ml.kg(-1).min(-1) in 4071 males and 34.3 +/- 4.3 ml.kg(-1).min(-1) in 4367 females. A graded dose-response relationship was observed in males and females between the frequency of participation in brisk exercise and VO(2peak). Similar dose-response relationship was also observed in overweight and obese persons, although the level of VO(2peak) was lower in persons with increased BMI. At age 31, very low levels of VO(2peak) seemed to be associated with a combination of infrequent participation in brisk exercise and increased BMI. These reference values can be used in the interpretation of fitness test results and in physical activity counselling.