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 (r = 0.491, P < 0.001). Among demographic details, only female sex (P < 0.001) was significantly associated with lower 1‐RM values. Further, after adjusting for age and sex, lower value of log(10) 1‐RM knee extension was found to be significantly associated with malnutrition (P = 0.001), dementia (P = 0.016), depression (P = 0.047), frailty (Rockwood: P = 0.049; Fried: P = 0.011), and sarcopenia (P < 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.