Low one-repetition-maximum knee extension is significantly associated with poor grip strength, female sex, and various aging-related syndromes.

Objective: Muscle strength in older adults is usually measured according to grip strength, which demonstrates upper muscle strength only. In this study, we used one-repetition-maximum (1-RM) knee extension as a measure of lower limb strength and assessed its relationship with grip strength and various geriatric syndromes.

Methods: One hundred outpatients over the age of 65 years were recruited from a geriatric medicine center in India. The 1-RM knee extension was measured along with grip strength. Various geriatric conditions were measured, such as: nutrition (using the Mini Nutritional Assessment), cognition (Hindi Mental State Questionnaire), depression (5-item Geriatric Depression Scale), frailty (Fried and Rockwood models), and osteoporosis (dual-energy X-ray absorptiometry scan). Sarcopenia was diagnosed using the Asian Working Group for Sarcopenia criteria.

Results: The mean age of participants was 72.5 years with 69% of them male. Median values of 1-RM knee extension and grip strength were 2.29 (0.5-10.0) and 17.5 (0-78), respectively. The 1-RM knee extension had moderate correlation with grip strength ( = 0.491,  < 0.001). Among demographic details, only female sex ( < 0.001) was significantly associated with lower 1-RM values. Further, after adjusting for age and sex, lower value of log 1-RM knee extension was found to be significantly associated with malnutrition ( = 0.001), dementia ( = 0.016), depression ( = 0.047), frailty (Rockwood:  = 0.049; Fried:  = 0.011), and sarcopenia ( < 0.001).

Conclusion: The 1-RM knee extension has only moderate correlation with grip strength. A lower 1-RM knee extension value is significantly associated with female sex and various geriatric conditions, such as malnutrition, dementia, depression, frailty, and sarcopenia.