What is Known About Muscle Strength Reference Values for Adults Measured by Hand-Held Dynamometry: A Scoping Review.

Objective: To map the body of existing literature regarding reference values of maximal isometric muscle strength (MIMS) of upper and lower limbs obtained with handheld dynamometers (HHD) in healthy adults to identify potential gaps in the literature and specify future research needs.

Data Sources: A scoping review in which PubMed, EMBASE, CINAHL plus, PEDRO, and Cochrane databases were searched before May 1, 2020.

Study Selection: All studies using standardized HHD protocols for the purpose of establishing reference values in healthy adult population were included. Two independent reviewers completed an initial screening of article titles and abstracts, and the remaining articles were read in their entirety and screened according to the inclusion and exclusion criteria. Disagreements were discussed, with recourse to a third reviewer when needed.

Data Extraction: Data of the selected studies were extracted and charted by 2 independent reviewers using a tested data extraction grid to ensure method standardization. Data were subsequently merged to produce the complete final extracted data.

Data Synthesis: Titles and abstracts of 4015 studies were screened, 46 articles were fully reviewed, and 9 manuscripts were selected for the final analysis. A large variability exists between protocols used for muscle testing in terms of type of device, measurement units, subject positioning, and muscle groups tested.

Conclusion: The existing literature regarding HHD reference values of MIMS is scarce and presents gaps notably relating to strength units and well-described protocols with known psychometric properties, despite the development and increased availability of high quality HHD. This observation emphasizes the critical need to develop reference values in manual dynamometry in adults to optimize the use of manual dynamometry for diagnostic and prognostic decisions.