Sex- and Age-Specific Centile Curves and Downloadable Calculator for Clinical Muscle Strength Tests to Identify Probable Sarcopenia

OBJECTIVE: Identifying muscle weakness and probable sarcopenia using strength tests requires reference data. This study aimed to provide age- and sex-specific normative data for grip strength and common variations of the Sit-to-Stand (STS) test: time to complete 5 stands (5x-STS) and number of stands completed in 30 seconds (30s-STS). Predictors of test performance were also explored. METHODS: Dominant hand grip strength was assessed in adults (age = 18-80 years) using a digital dynamometer, and 5x-STS and 30s-STS performance were assessed synchronously during a single 30-second test. Sex-specific centile curves were generated using the lambda-mu-sigma method. RESULTS: Data from 2301 participants (female = 1682, male = 619) were included. Peak median grip strength occurred in female participants at 33.9 years of age (27.9 kg) and in male participants at 37.6 years of age (47.2 kg). 5x-STS and 30s-STS performance peaked at the youngest age (18.0 years) in both female participants (8.16 seconds and 17.2 repetitions) and male participants (8.02 seconds and 17.7 repetitions). Test performances were lowest for all tests at the oldest age in the database. Predictors of better test performance included lower age and higher self-reported physical functioning and appendicular skeletal muscle mass, to name a few. White participants had better performance than Black participants on the STS tests. CONCLUSION: The generated centile curves reveal the pattern of change in muscle strength for tests recommended to identify probable sarcopenia. The curves can be used in rehabilitation to assess an individual's performance relative to sex- and age-specific norms. To aid use of the data, a downloadable Excel-based calculator is provided to compute participant-specific percentiles, z scores, and t scores for each outcome and plot performance on the centile curves. IMPACT: Physical therapists have an important role in identifying and treating individuals with sarcopenia and other causes of muscle weakness. The reference data provided for common clinical muscle strength tests provide therapists an ability to assess an individual's relative performance. LAY SUMMARY: Knowing the normal or expected strength for an individual's age and sex is essential to identifying muscle weakness. This study provides age- and sex-specific normal values for hand grip strength and sit-to-stand tests in adults aged 18 to 80 years.