Inclusion of blood lactate O2 equivalent in the VO2-intensity regression at level and 10.5% grade running

Abstract This study aimed to analyze the influence of adding blood lactate ([La-]) energy equivalent (Eq) to the VO2 measurements during running exercise at different grades (0% and 10.5%) in order to estimate energy cost of running. Thirteen male highly-trained middle- and long-distance runners (age 28.1 ± 4.2 years; stature 1.75 ± 0.07 m; body mass 65.2 ± 4.9 kg; and maximal oxygen uptake 70.3 ± 4.9 ml∙kg-1 ∙min-1 ) volunteered after medical approval and performed two treadmill tests (0% and 10.5% grade) which included several bouts at a constant speed. Individual VO2-speed regressions were determined for each subject and alternative regressions were established by adding an energy equivalent of 3 ml O2 Eq∙kg-1 ∙mM [La-] to the mean VO2 values. No significant interaction between [La-] O2 equivalent inclusion and grade running was found. Results of within-subjects ANOVAs indicated a significant effect of [La-] inclusion in the regression slope and in the estimated energy cost of running at both level and grade running. However, the obtained effect sizes suggest that this effect is considerably higher at level compared with grade running. These findings indicate that the inclusion of [La-] measurements in VO2-intensity regression estimates at sub maximal running should be considered when testing highly trained runners on the treadmill.