Figure 2.

Linear regression, polynomial regression with second-order term, and restricted cubic splines (RCS) regression analyses with Cooper’s 12-minute run score as outcome variable and body mass index (BMI) as predictor variable among 1,629 participants in the “From a boy to a man” study, born in 1981 in Finland. In the RCS regression model, knots were placed at BMI values of 18.5, 25, and 30. Akaike Information Criterion (AIC) and R-squared (R²) values were calculated separately for each model. A = All subjects, B = Non-smokers, C = Occasional smokers, D = Regular smokers.