Mixed

A preloaded 10-km treadmill time trial (90-min preload at 65% VO2max followed by a 10-km race) is highly reproducible for measuring endurance performance in trained runners, with a within-subject coefficient of variation of 1.00%.

For researchers studying endurance performance, using a 90-minute preload run at 65% of max oxygen uptake followed by a 10-km time trial on a treadmill provides a highly reliable measure of performance (CV ~1%). To achieve this reliability, you must strictly control the participants' diet (high-carb, low-fat) for 24 hours prior, provide a standardized breakfast 3 hours before the test, and ensure fluid intake is consistent between testing sessions. This protocol is particularly useful for detecting small changes in performance due to nutrition or training interventions in trained runners.