Predicting Cardiorespiratory Fitness in Female Soccer Players: The Basque Female Football Cohort Study

PURPOSE: To develop gender-specific operational equations for prediction of cardiorespiratory fitness in female footballers. METHOD: Forty-eight semiprofessional female footballers performed an intermittent progressive maximal running test for determination of fixed blood lactate concentration (FBLC) thresholds. Relationships between FBLC thresholds and the physiological responses to submaximal running were examined. Developed equations (n = 48) were compared with equations previously obtained in another investigation performed in males (n = 100). RESULTS: Submaximal velocity associated with 90% maximal heart rate was related to FBLC thresholds (r = .76 to .79; P < .001). Predictive power (R2 = .82 to .94) of a single blood lactate concentration (BLC) sample measured at 10 or 11.5 km·h-1 was very high. A single BLC sample taken after a 5-minute running bout at 8.5 km·h-1 was related to FBLC thresholds (r = -.71; P < .001). No difference (P = .15) in the regression lines predicting FBLC thresholds from velocity associated with 90% maximal heart rate was observed between the female and male cohorts. However, regressions estimating FBLC thresholds by a single BLC sample were different (P = .002). CONCLUSIONS: Velocity associated with 90% maximal heart rate was robustly related to FBLC thresholds and might serve for mass field testing independently of sex. BLC equations accurately predicted FBLC thresholds. However, these equations are gender-specific. This is the first study reporting operational equations to estimate the FBLC thresholds in female footballers. The use of these equations reduces the burden associated with cardiorespiratory testing. Further cross-validation studies are warranted to validate the proposed equations and establish them for mass field testing.