ABSTRACT The oxygen equivalent of blood lactate accumulation (ΔLa) is commonly expressed relative to body mass (BM), yet BM includes adipose tissue which does not substantially contribute to glycolytic energy production nor lactate distribution space and may confound sex comparisons. We examined whether replacing BM with fat‐free mass (FFM) (i) improves the correspondence between calculated glycolytic work and 15‐s sprint work and (ii) attenuates sex differences in the work–lactate relationship. Seventy‐one trained cyclists (48 men, 23 women) performed a 15‐s all‐out seated cycling sprint on a Cyclus2 ergometer. Blood lactate was sampled at rest and repeatedly for 8 min post‐sprint; ΔLa was defined as peak minus pre‐exercise lactate. Glycolytic work (W Gly ) was calculated using an oxygen‐equivalent approach with ΔLa scaled to either BM or FFM. General linear models included glycolytic work, sex, and 15‐s work. Men exhibited higher 15‐s work and ΔLa than women, but the slope of the relationship between W Gly and 15‐s work did not differ by sex for either BM or FFM. Regression models using FFM explained slightly more variance in 15‐s work than BM ( R 2 = 0.79 vs. 0.75). Adding sex improved model fit for both formulations ( R 2 = 0.85 and 0.85, respectively), indicating primarily an intercept effect rather than a slope difference. Replacing BM with FFM provides only a small improvement in explaining 15‐s work and does not reveal sex‐specific differences in the work–lactate slope. Thus, the lactate oxygen equivalent appears sex‐invariant while FFM‐based scaling may still be preferred for a more physiologically grounded estimate of W Gly .
Meixner et al. (2026) studied this question.