Normative values and predictive equations of hand-held dynamometry for upper limb muscles in healthy adults

The aim of this study was to establish comprehensive normative values and generate robust predictive equations for isometric upper limb muscle strength using hand-held dynamometry (HHD) in healthy adults aged 18 to 80 years. A cross-sectional multicenter study was conducted with 210 healthy volunteers aged 18 to 80 years. Participants were rigorously screened to exclude cognitive impairment, acute musculoskeletal symptoms, or systemic conditions that could influence strength. Participants underwent standardized assessment of isometric strength using a handheld dynamometer for 10 key upper limb muscle groups (dominant and non-dominant limbs), and maximal isometric strength (kgf) of each muscle group was recorded. Primary analytical outcomes included age- and sex-specific reference values and derived predictive equations for strength. Novel predictive equations were successfully developed for all 10 upper limb muscle groups from this diverse sample. A very good correlation (r2 range: 0.62-0.77, P<0.001) was observed between direct HHD measurements and the proposed equations. Importantly, these new equations demonstrated superior predictability for this population compared to previously published North American reference equations. This study provides the first comprehensive set of age- and sex-specific normative values and predictive equations for isometric upper limb muscle strength via HHD in healthy adults. These invaluable normative data enable rehabilitation professionals to objectively assess strength, identify weakness early, and enhance treatment monitoring, thus strengthening evidence-based practice in physical medicine and rehabilitation.