Track and Treadmill Lactate Assessments Are Not Interchangeable for Training Prescription in Elite Distance Runners.

This study characterized physiological and biomechanical differences between track and treadmill running in elite distance runners at race-relevant intensities. Nine male Tier 4 runners (5000 m personal best: 13:35 ± 0:03 min:s; 10 000 m: 27:44 ± 0:06 min:s) completed six-stage incremental tests (286-375 m·min-1) on both a 300-m track and a motorized treadmill (0% grade) in a randomized crossover design. Blood lactate concentration was significantly higher during track running across all stages (p < 0.001, η2p = 0.784), with the difference increasing progressively from 1.0 mmol·L-1 at stage 1 to 3.7 mmol·L-1 at stage 6 (condition × stage interaction: p < 0.001, η2p = 0.624). Running velocities at fixed blood lactate concentrations were lower during track running at both 4 mmol·L-1 (329.6 ± 4.3 vs. 345.1 ± 4.1 m·min-1; p = 0.008) and 6 mmol·L-1 (344.2 ± 3.1 vs. 359.4 ± 3.8 m·min-1; p = 0.012), corresponding to velocity adjustments of approximately 7-8 s·km-1. Ground contact times were significantly longer during track running at high intensities. In eight runners with 10 000 m season bests, track-based velocity at 6 mmol·L-1 demonstrated superior predictive validity (r = -0.973, R2 = 0.948, p < 0.001) compared to treadmill assessment (r = -0.695, R2 = 0.483, p = 0.061). Track and treadmill lactate assessments are not interchangeable for training prescription; track-based assessment should be prioritized when feasible. At threshold speeds typical of this cohort (~21 km·h-1), treadmill-derived threshold velocities exceeded track-derived values by approximately 7-8 s·km-1. Practitioners should apply this correction in both directions: when transferring treadmill-derived zones to track training, prescribed track velocities should be reduced by this margin; conversely, to replicate equivalent track intensity on a treadmill, treadmill speed should be raised by the same amount. The required correction is speed-dependent and increases at higher running velocities.