Do Body Height and Leg Length Matter Equally? A Biomechanical Analysis of Obstacle Crossing in Young Adults

Obstacle crossing is a fundamental locomotor task that requires adaptation of gait and postural control. Obstacle height is commonly normalized to an individual's anthropometrics, most often leg length, but some studies use body height. However, it remains unclear how these two reference measures influence gait outcomes. Therefore, this study examined the effects of using body height versus leg length as reference measures for obstacle height normalization on temporal-spatial gait parameters, postural control, and kinematics in young adults. Thirty-two young adults participated in a cross-sectional study. Participants performed obstacle crossing at 10%, 20%, and 30% of both leg length and body height. Temporal-spatial gait parameters, center of mass (COM) displacement and velocity, and hip, knee, and ankle angles were recorded using a 3D motion capture system. Repeated measure ANOVA was applied to test differences across obstacle heights within each normalization method. When normalized to body height, significant differences across obstacle heights were observed for crossing velocity, crossing time, trailing-limb crossing stride length, leading- and trailing-limb crossing stride time, and leading- and trailing-limb toe clearance, and hip, knee and ankle angles. In contrast, normalization to leg length revealed significant differences only in crossing time, trailing-limb crossing stride time, and leading- and trailing-limb toe clearance, and hip and knee angles. Neither normalization method showed significant effects on COM displacement or velocity. In conclusion, both normalization methods revealed similar overall trends, but body height normalization yielded a greater number of significant temporal-spatial gait changes compared to leg length normalization. These findings suggest that the choice of normalization method can influence the interpretation of gait outcomes and should be considered carefully in both research and clinical settings.