Influence of Thigh and Shank Lengths and Ratios on Kinematic and Kinetic Characteristics of the Knee Joint During Barbell Back Squat

The barbell back squat, a prevalent lower-limb resistance exercise characterized by a closed kinetic chain and multi-joint movement, results in the greatest knee joint range of motion. Variations in thigh and shank lengths and their ratios may influence knee joint mechanics. This study investigated the effects of thigh and shank lengths and their ratios on knee kinematics and kinetics during the barbell back squat. Fifty resistance-trained adult men participated. Kinematic and kinetic data were collected using an eight-camera motion capture system and two force plates. Correlation and simple linear regression analyses were conducted to evaluate the relationships between thigh and shank length parameters and knee joint mechanics. Greater thigh length was significantly associated with increased anterior knee displacement and knee extension moment. Additionally, longer shank length and a higher shank-to-thigh ratio were associated with greater knee abduction and internal rotation angles. Consequently, increased thigh length may contribute to greater anterior knee displacement, while increased shank length may be associated with increased knee abduction and internal rotation. Accordingly, trainers and trainees should evaluate individual thigh and shank lengths. For participants with relatively longer shank and thigh segments, compensatory knee movements should be closely monitored to mitigate the risk of musculoskeletal injuries.