Characterization Of Cardiorespiratory Fitness In Female Athletes: The Importance Of The Prediction Equation Used

Precise characterization of cardiorespiratory fitness (CRF) is dependent on comparing measured peak pulmonary oxygen uptake (V̇O2peak) against accurate reference values. Several equations exist that predict V̇O2peak. However, their accuracy relative to directly measured values in specific populations, including female athletes, is not well known. PURPOSE: To compare directly measured V̇O2peak against reference values obtained from five different prediction equations in female athletes. METHODS: 53 female athletes (age 39 ± 17 years; BMI 23.8 ± 4.1 kg·m2) underwent a maximal cardiopulmonary exercise test (Mayo Clinic Treadmill Protocol). Directly measured V̇O2peak was compared to predicted values from five equations: FRIEND Registry 2022 (FR1), FRIEND Registry 2017 (FR2), ACSM 2017 (ACSM1), ACSM 2010 (ACSM2), and Wasserman-Hansen 2005 (WH). Bland-Altman plots and one-way repeated measures ANOVA with Bonferroni adjustment were used to assess agreement and differences, respectively, between measured and predicted values for V̇O2peak. RESULTS: Measured V̇O2peak was 35.6 ± 9.0 mL·kg−1·min−1. Predicted V̇O2peak for each reference equation was FR1 = 31.8 ± 8.1 mL·kg−1·min−1; FR2 = 32.4 ± 8.0 mL·kg−1·min−1; ACSM1 = 36.6 ± 8.6 mL·kg−1·min−1; ACSM2 = 46.3 ± 8.7 mL·kg−1·min−1; WH = 29.9 ± 7.0 mL·kg−1·min−1. Bias ± standard deviation for measured vs. predicted V̇O2peak was FR1 = 3.8 ± 6.7 mL·kg−1·min−1; FR2 = 3.3 ± 6.6 ACSM1 = −0.9 ± 7.7; ACSM2 = −10.6 ± 7.4; WH = 5.7 ± 6.4 (Figure 1). Measured V̇O2peak was significantly lower vs. predicted V̇O2peak from ACSM2 (P < 0.001) but greater vs. predicted V̇O2peak from WH (P = 0.002). Measured V̇O2peak was not statistically different compared to predicted values from FR1, FR2, and ACSM1. CONCLUSIONS: The ACSM2 and WH equations to predict V̇O2peak may over- and under-estimate CRF, respectively, in female athletes. Precision characterization of CRF in female athletes is likely dependent on the V̇O2peak prediction equation used.