Author(s): MOUGIN, L., BAILEY, S.J., JONES, A.M., JOYNER, M.J., MEARS, S.A., PEARCE, R., ZANINI, M., Institution: LOUGHBOROUGH UNIVERSITY, Country: UNITED KINGDOM, Abstract-ID: 1365

INTRODUCTION:
Endurance performance can be predicted by maximal oxygen uptake (V̇O2max), its fractional utilisation at lactate threshold (FULT), and exercise economy (1). These variables are used to estimate speed or power at lactate threshold (LT) and lactate turnpoint (LTP), which serve as performance proxies (1, 2). This study examined the relationships between these variables in a large cohort of runners and cyclists and quantified their relative contributions to performance prediction.
METHODS:
495 runners (105 females) and 393 cyclists (42 females) completed incremental exercise tests to determine V̇O2max (running [R]: 56 ± 9 mL/kg/min, 3.94 ± 0.75 L/min; cycling [C]: 52 ± 10 mL/kg/min, 3.99 ± 0.66 L/min), economy (R: 220 ± 18 mL/kg/km; C: 14.7 ± 1.5 mL/min/W), FULT (R: 78 ± 5%; C: 70 ± 6%), FULTP (R: 88 ± 6%; C: 84 ± 6%), and speed or power at LT (R: 12.0 ± 2.2 km/h; C: 190 ± 39 W) and LTP (R: 13.9 ± 2.4 km/h; C: 240 ± 45 W). The test consisted of 4-min stages with increments of 0.5-1.0 km/h (R) or 10-30 W (C) depending on participant’s training background, followed by 15-20 min rest and a ramp test lasting 8-12 min. LT and LTP were defined as the first rise in blood lactate concentration (B[La-]) from baseline (+0.5 mmol/L) and as a rapid and sustained increase in B[La-] (+1.5 mmol/L) between two subsequent stages, respectively. Multiple correlations were assessed using linear models, with P-values corrected for multiple testing using the Holm-Bonferroni procedure. Multiple linear regression models were used to estimate the contribution of physiological determinants to performance proxies. Significance was set as P ≤ 0.05.
RESULTS:
Speed or power at LT and LTP correlated strongly and positively with V̇O2max (R² = 0.65-0.77; P<0.001), and inversely with economy (R² = 0.24-0.26; P < 0.001). In contrast, smaller relationships were observed with FULT (R² ≤ 0.04; P = 0.01-0.05) and FULTP (R² ≤ 0.01; P = 0.01-0.09). Regression models estimating LT and LTP from physiological determinants showed very strong agreement with measured performance proxies (LT: R² = 0.98-0.99, LTP: R² = 0.94-0.97; P < 0.001), indicating high consistency in their relative contribution to performance proxies. V̇O2max contributed most to performance proxies in both running (72-76%) and cycling (65-73%) followed by exercise economy (R: 20-22%, C: 21-24%), with marginal but significant contributions from FULT or FULTP (R: 4-6%, C: 6-11%). Similar results were found between sexes.
CONCLUSION:
These results are the first to indicate that, across a large and heterogeneous cohort of runners and cyclists, and between sexes, V̇O2max and economy collectively predict ~95% of speed or power at LT and LTP, and by extension endurance performance. Conversely, FULT or FULTP showed limited value in explaining between-athlete performance differences, confirming recent cross-sectional findings (3).

1. Joyner, 1991, J. Appl. Physiol.
2. Jones et al., 2021, J. Appl. Physiol.
3. Johansen et al., 2025, Int J Sports Physiol Perform