Maximal glycolytic flux modulates metabolic thresholds independent of maximal oxygen uptake.

PURPOSE: This study examined how maximal glycolytic flux, indexed by the peak lactate accumulation rate (vLapeak) from a 15-s sprint, relates to lactate- and gas-exchange derived endurance thresholds at a given V̇O2max in trained cyclists.

METHODS

Fifty cyclists (30 men, 20 women) completed two laboratory visits: a ramp test with verification to determine V̇O2max, and on a separate day, a 15-s all-out sprint with repeated post-exercise capillary blood sampling to determine peak lactate accumulation (ΔLa) and derived vLapeak, followed by a 3-min step-increment test with lactate and gas-exchange measurements.

RESULTS

Partial correlations controlling for V̇O2max revealed moderate-to-strong negative associations between vLapeak and selected lactate- and gas-exchange-derived thresholds (r = - 0.37 to - 0.59, p < 0.01), whereas absolute and relative 15-s work showed consistently weaker or no relationships (r = 0.06 to - 0.48). No association was observed between vLapeak and peak fat oxidation. In general linear models, adding vLapeak to models with V̇O2max and sex as predictors significantly increased the explained variance in threshold power (ΔR2 ≈ 0.06 to 0.20). Sex contributed additional but consistently smaller effects.

CONCLUSION

These findings indicate that the power output at several metabolic thresholds originates from the interaction of maximal oxidative and glycolytic flux. As such, vLapeak seems to be a promising parameter that complements traditional measures like V̇O2max and helps to improve metabolic profiling and exercise prescription. However, longitudinal studies are needed to verify these findings.