Familiarization is widely recommended before exercise performance testing to improve measurement consistency and reduce learning effects. However, practical constraints often limit researchers to a single-or no-familiarization session, raising the possibility that improvements observed following an intervention may partially reflect increased familiarity with the testing procedure rather than genuine physiological adaptations. This issue may be particularly relevant for time-to-exhaustion (TTE) protocols, which have been reported to exhibit greater between-session variability than self-paced endurance tests.

This exploratory analysis examined the magnitude of the familiarization effect during treadmill TTE testing by comparing a familiarization trial with a subsequent experimental trial. Linear mixed-effects models will be used to evaluate changes in TTE performance while accounting for pre-exercise fatigue and recovery, and between-session agreement was assessed using intraclass correlation coefficients and Bland-Altman analysis.