Lower extremity muscle strength is a factor in the early stage of development of locomotive syndrome in Japanese American women: A cross-sectional study

Background: Obesity and lower extremity muscle strength (LEMS) is a factor in the development of locomotive syndrome (LS), but the influence of gender differences on its development has not been clarified. We aimed to determine whether obesity and LEMS are associated with LS by sex, using a Japanese American population with a high prevalence of obesity. Methods The study was a cross-sectional study of 564 people living in Los Angeles, United States of America. The LS stage was graded using the 25-question Geriatric Locomotive Function Scale. The LEMS was determined by the knee extension force (KEF). Logistic regression analysis was performed to investigate the relationships between LS stage and KEF, age, and obesity-related parameters. Results No significant differences were found in the prevalence rates of non-LS, stage 1 LS, and stage 2 LS among the different age groups for men. In contrast, significant differences were observed in the LS prevalence rates the different age groups for women. In men, KEF was significantly lower in the stage 2 LS group than in the non-LS group. Conversely, in women, KEF was significantly lower in the stage 1 LS and stage 2 LS groups than the non-LS group. KEF was significantly associated with LS in the stage 2 LS group in men, while age and KEF were significantly associated with LS in the stage 1 LS and stage 2 LS groups in women. Conclusions KEF was found to be a factor in the development of stage 2 LS in men and stages 1 and 2 LS in women. Therefore, efforts to prevent muscle weakness in KEF from the early stage of LS in women are considered a necessary intervention.