Differences in hip and knee muscle strength between successful and unsuccessful performances of the single leg sit to stand test from a 20-cm-high box in healthy young adults

[Purpose] To investigate differences in knee and hip muscle strength between successful and unsuccessful single leg sit to stand tests from a 20-cm-high box (SLST 20) in healthy young adults. [Participants and Methods] Sixty-six lower limbs from 33 healthy adults (20 males, 13 females; mean age 25.4 ± 3.4 years) were classified into successful and unsuccessful groups. Isokinetic strength of the knee (flexion/extension at 60°/s) and hip (flexion/extension/abduction/adduction at 30°/s) was measured. Statistical analyses included t-tests, Kruskal-Wallis tests, and analysis of covariance (ANCOVA) using sex as a covariate. Stratified analyses were also performed. [Results] The successful group had significantly greater strength in knee flexion/extension, hip flexion, and hip adduction. ANCOVA revealed that knee flexion and extension were significantly associated with SLST 20 performance, whereas hip strength was not, after adjusting for sex. Among females, hip adduction strength was significantly greater in the successful group, with no significant difference observed in males. [Conclusion] Knee strength is crucial for SLST 20 performance, and hip adduction strength may be important, particularly in females. Therefore, sex-specific assessments and training strategies should be considered in clinical practice.