A Novel Method of Clinical Strength Assessment: Reliability and Validity of a Crane Scale for the Quadriceps and...

Hedt, C, Silva, C, Lambert, B, Goble, H, Armond, D, Bowden, M, and McCulloch, P. A novel method of clinical strength assessment: reliability and validity of a crane scale for the quadriceps and hamstrings. J Strength Cond Res XX(X): 000-000, 2026-This study evaluated a low-cost crane scale (CS) for quadriceps and hamstring isometric strength testing versus an isokinetic dynamometer (IKD) and a handheld dynamometer (HHD). Twenty-two healthy adults completed 2 sessions ≥72 hours apart, performing 3 5-second maximal isometric contractions per device, per tester, in standardized seated positions (quadriceps 90° flexion; hamstrings 60°). Outcomes were torque (N·m), coefficients of variation (CV), and intra-/interobserver reliability (ICC). A one-way repeated-measures ANOVA with Bonferroni adjustments compared devices; ICCs (2-way mixed) with 95% CIs quantified reliability; α (ρ) was set at 0.05. For knee extension, CS produced mean and peak torque comparable with IKD, whereas HHD was significantly lower than both CS and IKD (p < 0.001). For knee flexion, CS exceeded HHD (p = 0.023) with no significant difference from IKD. Measurement variability (CV) was lower for CS and IKD than HHD in extension (p < 0.001); IKD showed the lowest variability in flexion (p ≤ 0.010). Inter- and intraobserver reliability were excellent (ICC > 0.70) across devices, with CS demonstrating the highest ICCs and narrowest confidence intervals. The CS demonstrated strong agreement with IKD and superior reliability relative to HHD, supporting its potential use as a practical, portable alternative for objective lower-extremity strength assessment in applied settings.