DATASET FOR STUDY: Intra-visit and inter-visit reliability of myotonometry-based stiffness assessment in biceps femoris and semitendinosus muscles

Objective: To determine the intra-visit and inter-visit (test–retest) reliability of myotonometry-based muscle stiffness assessment at proximal and distal sites of the biceps femoris (BF) and semitendinosus (ST). Methods: Twenty-two healthy adults (9 women, 13 men) attended two testing sessions separated by 7–10 days. At each visit, three consecutive stiffness measurements were obtained at proximal and distal sites of BF and ST using the MyotonPRO device. Relative reliability was assessed using a two-way mixed-effects intraclass correlation coefficient with absolute agreement (ICC(3,1)) and 95% confidence intervals (CI). Absolute measurement error was quantified using the typical error (TE) and coefficient of variation (CV). Results: Intra-visit reliability was excellent across all sites (ICC = 0.98–0.99; CV = 2.19–3.53%). Test-retest reliability ranged from good to excellent (ICC = 0.87–0.93). Test-retest CV values ranged from 6.61% to 10.10%, with the highest relative error observed at the proximal ST site. Lower bounds of 95% CI for ICC remained above 0.72 across sites. Bland–Altman analysis revealed small, non-significant biases between sessions and no evidence of proportional bias. Conclusions: MyotonPRO-derived stiffness measurements of the BF and ST demonstrate excellent within-session and good-to-excellent between-session reliability in healthy young adults. Measurement error was low, supporting the use of site-specific hamstring stiffness assessment for research and monitoring purposes.