Salter J, Forsdyke D, Dawson Z, Rymer J, Walsh L, Mundy P. Reliability and Sensitivity of Using Isometric Strength and Sprint Speed Measures in Adolescent Female Athletes. J Strength Cond Res. 2025;39(4):418-426. doi:10.1519/JSC.0000000000005029
The aim of this study was to establish the reliability and sensitivity of isometric mid-thigh pull (IMTP) and sprint speed (5 m, 40 m, and maximal sprint speed) in adolescent women, before exploring the stability of this across maturation to provide maturity-specific benchmarks. A total of 147 female athletes (age: 13.8 ± 2.8 years; stature: 157.1 ± 13.1 cm; body mass: 51.2 ± 15.3 kg; percentage of predicated adult height: 94.3 ± 6.6) performed IMTP and sprint trials on 2 occasions, separated by 7 days. Within- and between-session reliability was determined using intraclass correlation coefficient (ICC), coefficient of variation, and Bland-Altman limits of agreement, with sensitivity detected by signal-to-noise ratios for small (SWC 0.2 ) and moderate (SWC 0.5 ) worthwhile change. A between-group analysis of variance and Cohen’s d -effect sizes determined differences between biological maturity groups (pre-, mid-, and post-peak height velocity [PHV]). All isometric strength and sprint performance markers demonstrated either ” moderate ” or ” acceptabl e” within-session reliability, except for time to peak force (PF) and 40 m sprint. Despite metrics all having ” high ” or above ICC (0.55-0.98), only PF offered a ” good ” sensitivity when using SWC 0.2 , with most offering better sensitivity with SWC 0.5 . Noise was higher between sessions, resulting in ” poor ” signal-noise ratios, likely associated with the bias favoring retest trials. Reliability and sensitivity findings were consistent across maturational stages, demonstrating either ” moderate ” or ” acceptable ” reliability. There were clear differences between maturity groups for all measures, particularly between mid-PHV and post-PHV. Practitioners can be assured that IMTP and sprint performance measures are reliable within this population but require thorough familiarization processes before confidence in interpreting meaningful changes.