The effect of body weight on joint torques in teenagers: Investigation of sit-to-stand movement

Background: Obesity is becoming more common in the world. This causes various health problems, especially musculoskeletal disorders. Previous studies have examined the kinematic effects of increasing weight on joints. However, the mechanical effects of movement patterns have not yet been described. The aim of this study was to investigate joint torques in sit-to-stand movement in teenagers with a range of body mass indices (BMI). Methods: 20 participants (12?17 years old) participated the study. They were divided into 4 groups according to BMI. Participants performed sit-to-stand movements and the video was captured. Angular displacement, angular velocity, and angular acceleration were calculated for each joint. A four-degree-of-freedom link-segment model was created for a dynamic analysis of sit-to-stand. Joint torques were calculated using the inverse dynamic method. Findings: Overweight increases joint torques in hips, knees, and ankles. In obese participants with a BMI 36% higher than normal-weight participants, joint torques in hips, knees, and ankles were higher by 46, 48, and 33%, respectively. In underweight participants with a BMI 21% lower than normal-weight participants, joint torques in neck, hip, knee, and ankle were lower by 20, 30, 17, and 7%, respectively. Interpretation: Overweight participants have a different sit-to-stand movement pattern. Movement differences and overweight may cause an overload on joints.