Reliability and validity of hand-held dynamometer and hand-held sphygmomanometer for testing shoulder isometric external and internal rotator muscles strength

Background: Shoulder strength evaluation is a recommended procedure in musculoskeletal rehabilitation.
Aim: To examine hand-held sphygmomanometer (HHS) and hand-held dynamometer (HHD) intra- and inter-rater reliability during isometric shoulder external and internal rotation strength testing in prone rotation position in asymptomatic participants, and to compare these two testing modalities.
Design: Reliability study
Methods: A total of 20 asymptomatic participants (27.7±7.4 years; 77.1±10.1 kg) attended a strength assessment consisting of HHS and HHD tests. Reliability was assessed using the intra-class correlation coefficient (ICC) with 95% confidence intervals (CI), coefficient of variation (CV) with 95%CI, and standard error of measurement (SEM). Pearson correlation and linear regression analysis were used to compare HHS and HHD testing modalities.
Results: “Good” to “excellent” intra (ICC range = 0.896 to 0.979) and inter-rater reliability scores (ICC range = 0.850 to 0.978) were displayed during both HHS and HHD tests during internal and external rotation strength assessments. Linear relationships between HHS and HHD measures were found, with coefficients of determination (R2) ranging between 0.60 to 0.79.
Conclusion: HHS and HHD resulted to be reliable strength assessment modalities for clinical practice. These assessment modes can be equally valid in assessing intra and inter-limb asymmetries in isometric shoulder rotation strength. The affordability and availability of HHS in ordinary clinical settings can facilitate its implementation in musculoskeletal practice.