Estimation methods to detect changes in cardiorespiratory fitness due to exercise training and subsequent detraining

Purpose To determine whether estimated maximal oxygen consumption ( eV̇O_2max ) can detect cardiorespiratory fitness (CRF) changes by behavioral modifications. This study compared changes in measured V̇ O 2max (m V̇ O 2max ) through exercise intervention with e V̇ O 2max using a multiple regression model (MRM) and linear extrapolation method (LEM). Methods A cross-sectional analysis involving 173 adults was conducted to establish an MRM by including age, sex, body mass index, questionnaire score, heart rate (HR) from step test, and m V̇ O 2max . Subsequently, 15 men participated in an intervention experiment comprising an 8-week, high-intensity interval training, followed by 8-week detraining, and completed anthropometric measurements, questionnaires, step tests, and m V̇ O 2max tests. m V̇ O 2max changes throughout the intervention were compared to e V̇ O 2max changes calculated using the MRM and LEM. The LEM used the HR during the step test with constant values (predetermined V̇ O 2 ), such as the Chester step test. Results Inclusion of the step test HR in a questionnaire-based MRM improved the estimation power, although the MRM underestimated higher m V̇ O 2max values. In the intervention, m V̇ O 2max increased by 20.0 ± 14.1