RESUMO
OBJECTIVE: This study explored the correlation between body mass index (BMI) and knee angle during ascending and descending stairs in healthy young adults. The hypothesis was that higher BMI would be associated with altered knee angles during stair ambulation. PATIENTS AND METHODS: Participants' (n = 43) demographic characteristics, including age, height, weight, BMI, leg preference, and thigh lengths, were recorded. Gait parameters, such as cycle duration, stride phase, velocity, and knee angles, were analyzed using Kinovea® software. Inferential statistical tests, including ANOVA, t-tests, and correlation analysis, were performed to explore the relationships and differences between variables. RESULTS: No significant effect of BMI on knee angle was found [ascending stairs: F (2, 40) = 0.75, p = 0.47; descending stairs: F (2, 40) = 0.58, p = 0.56]. However, gait parameters differed significantly, with shorter cycle duration during ascending stairs (M = 4.52 s, SD = 0.76 s) compared to descending stairs (M = 4.72 s, SD = 0.81 s). The stride phase varied across BMI categories [F (2, 40) = 3.82, p < 0.05], with the ideal weight group (M = 47.12%, SD = 3.21%) exhibiting a distinct stride phase. Positive correlations were found between knee angle and thigh length difference during ascending (r = 0.42, p < 0.05) and descending stairs (r = 0.38, p < 0.05). CONCLUSIONS: This study demonstrated that BMI did not significantly affect knee angle during stair ambulation. However, gait parameters such as cycle duration, stride phase, and velocity differed between ascending and descending stairs. The positive correlation between knee angle and thigh length difference suggests that individuals with more significant thigh length differences may exhibit larger knee angles during stair climbing. The findings of this study have clinical implications for rehabilitation programs and the design of assistive devices. Understanding the relationship between BMI, thigh length difference, and knee angle during stair climbing can help clinicians better assess and manage gait abnormalities in individuals navigating stairs.