Three-dimensional gait analysis of obese adults

Abstract

In recent years, obesity was considered as a global epidemic disease. There were over 300 million obese adults worldwide in 2000. This led to an increase in obesity-related morbidity and an imposition of a heavy burden on health care system. Obesity is related to several chronic diseases, such as hypertension, stroke, and various musculoskeletal disorders, in particular with lower limb problems. When it is widely believed that obesity causes increased load on lower limb joints, leading to joint pain or osteoarthritis, it has not been tested 3-dimensionally in a biomechanical study. Therefore, this study aimed to investigate the gait characteristics of obese adults and it is hoped that this information can give us a clue to whether the obesity leads to pathomechanics and enhance our knowledge about gait adaptations due to the obesity. Fifteen obese (BMI > 30.0 kg/m2) and fifteen non-obese adults (BMI from 18.5 kg/m2 to 22.9 kg/m2) participated in this study, but the data from one obese participant as well as one non-obese participant was excluded in the analysis due to the technical problem. A 10-m long walkway was equipped with 2 AMTI force plates and a Vicon 370 3-D Motion Analysis System to collect gait data of the 2 groups at standard and self-selected walking speeds. The two-way repeated measures ANOVA with mixed samples were applied to compare the gait performances between the two groups. The obese group walked slower with a shorter stride length, longer stance phase duration and double support period as well as greater knee internal rotation than the non-obese group at self-selected walking speed. They also walked with smaller hip extension during push-off at standard walking speed; greater ankle eversion, ankle abduction and hip internal rotation throughout the gait cycle, greater knee adduction during swing period, greater hip adduction in late stance, and smaller hip range of motion at both walking speeds. For the kinetic data, the obese subjects showed reduced vertical force peak and anterior (propulsive) force peak during late stance period. Besides, they had decreased peak ankle abductor moment and increased peak ankle inversion moment during push-off at self-selected walking speed; and decreased peak ankle plantarflexor moment at both walking speeds. The obese individuals also demonstrated reduction in peak power at the ankle and the knee in the transverse plane during late stance period, peak hip power in the sagittal and coronal planes during push-off, and peak hip power in the coronal and transverse planes during loading response. At standard walking speed, the obese groups walked with reduced peak of the ankle power during late stance period in transverse plane and increased peak of the knee power in the coronal plane at terminal swing. Most of the kinematic and kinetic adaptations in the obese group contributed to a slower walking speed in addition to the reduction in energy expenditure, stride length and swing duration to maintain the stability during normal walking. At standard walking speed, the obese group tended to increase cadence and reduce the stride length to maintain the walking speed and preserve the balance. In conclusion, the obese individuals may adapt their gait in response to their bulky bodies to maximize the stability; reduce their energy expenditure per unit time and maintain normal moments about knee during walking.