Rate of Force Development During Sit‐to‐Stand Movement Is Associated With Locomotive Syndrome Severity: A Cross‐Sectional Study

ABSTRACT Aim Locomotive syndrome (LS) is defined as reduced mobility due to locomotor dysfunction. The sit‐to‐stand (STS) movement is a fundamental daily activity, and biomechanical parameters derived from STS capture quantitative aspects of mobility. However, their association with LS severity remains unclear. We aimed to examine whether STS parameters are associated with LS severity in this cross‐sectional study. Methods We analyzed 1047 adults (619 males, 428 females; median age 54 years) who underwent musculoskeletal health screening. LS stage was classified into non‐LS, LS1, LS2, and LS3 using the stand‐up test, two‐step test, and the 25‐question Geriatric Locomotive Function Scale. STS performance was measured with the STS force analyzer, and three parameters were derived: maximum ground reaction force normalized to body weight (F/w), rate of force development normalized to body weight (RFD/w), and stabilization time (ST). Associations between LS stage and these parameters were assessed using ordinal logistic regression adjusted for age, sex, and body mass index. Results Among participants, 47.0% were non‐LS, 46.0% LS1, 5.8% LS2, and 1.1% LS3. Compared with non‐LS, both F/w and RFD/w were significantly lower in LS1 and LS2, while ST was significantly longer in LS1. In ordinal logistic regression analysis, only RFD/w remained significantly associated with LS stage after adjustment (odds ratio: 0.84; 95% CI: 0.76–0.94; p = 0.002). Conclusions Our findings revealed that only lower RFD/w was independently associated with LS severity, suggesting that RFD/w could complement conventional LS risk tests.