At the Core of Performance: Reliability and Validity of a Baseline Evaluation of Strength Test Core (BEST Core) Across Expertise Levels Using the K-Pull Dynamometer

The trunk muscles play a key role in spinal stability. This study developed and validated the Baseline Evaluation of Strength Test Core (BEST Core), assessing core strength through six flexion, extension, inclination, and rotation tasks. A total of 102 participants of different skill levels and genders completed the test twice, separated by at least 72 hours, using a K-Pull dynamometer (Kinvent®). BEST Core measured maximal (Fmax) and mean (Fmean) forces. Test-retest reliability was assessed by repeating the protocol, and discriminant validity by comparing performance among competition levels. Results showed significant differences between skill groups for both Fmax and Fmean (p < .001), confirming strong discriminant validity. Reliability was excellent, with intraclass correlation coefficients of 0.952 and 0.907, and no significant differences between sessions. These findings indicate that BEST Core is a valid and reliable field test for monitoring core strength and assessing injury risk in athletes.