Intra-Rater Reliability and Construct Validity of Hand-Held Dynamometry to Evaluate the Hip Adductor Squeeze Test in Elite Youth Football Players

Hip and groin injuries are common in elite football, and reduced isometric adductor strength has been identified as a key risk factor. Therefore, reliable and valid field-based methods for assessing hip adduction strength are essential for effective monitoring and injury prevention. This study aimed to evaluate the intra-rater reliability and construct validity of a hand-held dynamometer (HHD) compared with the ForceFrame (FFS) during the adductor squeeze test in elite youth football players. Thirty-eight male academy athletes completed two testing sessions four weeks apart, performing maximal isometric adductor squeezes using both devices. Relative reliability was assessed using intraclass correlation coefficients (ICC), and construct validity was evaluated using paired <i>t</i>-tests, Bland-Altman analysis, and linear regression. The HHD demonstrated excellent intra-rater reliability (ICC = 0.90, 95% CI: 0.82-0.95) and the FFS showed good reliability (ICC = 0.85, 95% CI: 0.71-0.92). Paired <i>t</i>-tests revealed no significant differences between devices, and regression analysis confirmed no proportional bias, indicating strong agreement and construct validity. These findings demonstrate that the HHD provides valid and reliable measurements of isometric hip adduction strength and may serve as a practical, portable, and cost-effective alternative to fixed dynamometry for field-based strength assessment, rehabilitation monitoring, and injury-prevention screening in elite football environments.