The use of a sphygmomanometer to measure shoulder isometric strength: a validity and reliability study

Abstract Introduction: A sphygmomanometer is an instrument commonly used to measure blood pressure that can potentially be used to objectively assess shoulder isometric muscle strength. Objective: To establish the criterion validity and the intra-rater reliability of the sphygmomanometer for the assessment of shoulder isometric muscular strength compared to the handheld dynamometer. To determine if there is a statistically significant difference for shoulder strength between dominant and non-dominant sides. Methods: A test-retest study design was developed, where a rater assessed shoulder flexion and abduction isometric strength of 13 healthy university students, using a commercially available sphygmomanometer and a handheld dynamometer. Results: The criterion validity of the sphygmomanometer was found to be good for both right and left shoulder flexion and abduction strength assessment (Pearson’s r = 0.90-0.97). The intra-rater reliability of the sphygmomanometer was calculated to be good for both right and left flexion and abduction (ICC = 0.96-0.99). The handheld dynamometer also showed good intra-rater reliability for each of the strength measures assessed (ICC = 0.94-0.98). Significant differences (p < 0.01) were identified between dominant and non-dominant sides for shoulder strength. Conclusion: A sphygmomanometer is a simple and easily accessible tool that provides clinicians with accurate objective values for isometric shoulder strength assessment.