A Reference Equation for Normal Standards for VO₂ Max: Analysis from the Fitness Registry and the Importance of Exercise National Database (FRIEND Registry)

Existing normal standards for maximal oxygen uptake (VO₂ max) are problematic because they tend to be population specific, lack normal distribution and portability, and are poorly represented by women. The objective of the current study was to apply the Fitness Registry and the Importance of Exercise: A National Data Base (FRIEND) Registry to improve upon previous regression formulas for normal standards for VO₂ max using treadmill testing. Maximal treadmill tests were performed in 7783 healthy men and women (20-79years; maximal RER >1.0) from the FRIEND registry and a separate validation cohort of 1287 subjects. A regression equation for VO₂ max was derived from the FRIEND registry and compared to the validation cohort and two commonly used equations (Wasserman and European). Age, gender, and body weight were the only significant predictors of VO₂ max (multiple R=0.79, R²=0.62, p<0.001). The equation for predicting VO₂ max was: [Formula: see text] Marked differences were observed in percentage predicted VO₂ max achieved between commonly used reference equations, particularly among women, overweight and obese subjects. In the validation sample, the FRIEND equation closely paralleled measured VO₂ max, with the validation group yielding a percent predicted VO₂ max of 100.4% based on the FRIEND equation. An equation for age-predicted VO₂ max derived from the FRIEND registry provided a lower average error between measured and predicted VO₂ max than traditional equations, and thus may provide a more suitable normal standard relative to traditional equations.