Within-session test specific calibration in the T-agility test

This study aims to determine the minimum familiarization threshold (test-specific calibration) required to measure true performance capacity in the T-agility test and to mathematically demonstrate the systematic bias during this process. The high performance variability observed in the initial trials of agility tests stems from a cognitive and neuromotor calibration process where the athlete attempts to adapt to the test boundaries and rules, rather than from physical inadequacy. Thirty-four youth athletes with team-sport backgrounds (age: 16.12 ± 0.81 years) who were entirely naive to the standardized T-test protocol were included in the study. To optimally minimize the effects of fatigue, the athletes performed 9 consecutive successful T-test trials with 4-minute full recovery periods between each repetition. The obtained data were analyzed using Repeated Measures ANOVA, Intraclass Correlation Coefficient (ICC), and Bland-Altman analysis. The results indicated that the athletes' performance times improved significantly from the first trial (T1) to the sixth trial (T6). However, no statistically significant difference was detected among the T6, T7, T8, and T9 measurements, indicating that performance stabilized during this 4-trial plateau phase. A substantial systematic bias of 2.89 seconds was found between the participants' initial trial (T1) and their achieved peak score (Tpeak). Consequently, to allow athletes to reflect their true agility levels with optimally minimized fatigue and the novice reaction, we strongly recommend completing a calibration process of at least 5 repetitions at the beginning of the test. Based on these findings, the '5+3 Protocol'—which involves regarding the first 5 trials as familiarization to be excluded, and recording the peak score (best of the subsequent 3 measurement trials) to accurately reflect the athlete's true capacity is highly recommended for coaches and testing specialists to maximize measurement reliability.