The Relationship between Gait Biomechanics and Body Mass Index

Abstract

Walking gait is one of the basic components of human movements. With the rising obesity epidemic and implied health complications, it is pertinent to examine the relationship between body mass index and the joint torques and powers at the hip, knee, and ankle joints required to produce gate. The purpose of this study was to identify the relationships between ground reaction forces, joint torques, and joint powers at the hip, knee, and ankle and BMI in a group of people with BMIs ranging from 18-44 kg/m², while walking at a self-selected normal speed and at a safe self-selected maximum speed. We proposed a direct relationship between BMI and ankle torques and powers. Additionally, we proposed that hip and knee joint torques and powers would have a direct relationship to BMI up until approximately 35 kg/m² at which point individuals would begin to modulate their hip and knee joint torques and powers to mimic those used by healthy individuals. Gait biomechanics were collected for twenty-one healthy adults with BMI between 18 kg/m² and 44 kg/m² using an eight-camera Qualysis motion capture system and evaluated using Visual 3D. Each subject was tested while walking at a normal speed and a safe-maximum speed. The data showed a statistically significant relationship between maximum hip extensor torque at both a normal speed and a safe-maximum speed. No significant relationships were found between knee torques or powers and BMI. Maximum ankle plantarflexor torques and maximum positive ankle powers were found to be significantly correlated with BMI for both speeds. Additionally, first and second maximum ground reaction forces and maximum braking and propulsive forces were found to be significantly correlated with BMI at both speeds. We were unable to fully evaluate the specific hypothesis due to an inadequate sample size however, our results suggest that further investigation may support the hypothesis. Additionally, our subject sample was largely skewed towards females. We intend to continue subject recruitment in order to wholly test our original hypothesis as well as evaluate possible differences between the gait biomechanics of Class III obese males and females.