Normative reference values for estimated cardiorespiratory fitness in apparently healthy British men and women

Objectives: To develop normative reference standards for estimated cardiorespiratory fitness (eCRF) measured from treadmill-based incremental exercise testing in ~12 000 British men and women. Methods: Cross-sectional study using retrospectively collected eCRF data from five preventative health screening clinics in the United Kingdom. Reference centiles were developed using a parametric approach by fitting fractional polynomials. We selected the ‘best’ powers by considering both the smallest deviance, and clinical knowledge from the following set of a priori decided powers (-2,-1,-0.5, 0, 0.5,1,2,3). A series of fractional polynomials (FPs) were investigated with three-parameters (median, standard deviation and skewness). The following reference centiles were plotted (3, 5, 10, 25, 50, 75, 90, 95, 97). Results: We included 9 204 males (median [25th,75th centiles] age 48 [44, 53] years; BMI 27 {25, 29] kg∙m-2; peak VO2 36.9 [30.5, 44.7] ml∙kg-1∙min-1) and 2 687 females (age 48, [41, 51] years; BMI 24 {22, 27] kg∙m-2; peak VO2 36.5 [30.1, 44.8] ml∙kg-1∙min-1) in our analysis to develop the normative values. Conclusion: Reference values and nomograms for eCRF were derived from a relatively large cohort of preventative health care screening examinations of apparently healthy British men and women. Age- and sex-specific eCRF percentiles were similar to data from international cohort studies. The adoption of submaximal exercise testing protocols reduces individual risk when exercise history is unknown and testing is conducted in a community-based setting. Our findings can be used by health professionals to help guide clinical decision making.