Reference values for and cross-validation of time to exhaustion on a modified Balke protocol in Norwegian men and women

Abstract

The aims of the present study were to provide reference values for time to exhaustion (TTE) on a modified Balke treadmill protocol, and to perform a cross-validation of TTE as a measure of maximal oxygen consumption (VO_2max ), in Norwegian men and women 20-85 years of age. Reference values for TTE were derived from a national sample of 765 subjects. An additional sample of 119 subjects was included in the cross-validation (total n = 884), where prediction equations for VO_2max was established. A decline in TTE was seen with increased age. Prediction of VO_2max in an independent dataset (n = 319) resulted in a R² = 0.78 and standard error of the estimate = 4.55 mL/kg/min. The observed-predicted bias was small (mean difference <1.24 mL/kg/min), whereas random error was considerable (95% limits of agreement ± 7.11-9.70 mL/kg/min) across age in both men and women. Despite limitations concerning the prediction of VO_2max on an individual level, TTE from the Balke protocol is a good measure of aerobic fitness in adults across a range of settings, and could be evaluated according to the suggested reference values.

Keywords: Maximal graded treadmill protocol; VO2max; aerobic capacity; validity.