Sagittal and frontal plane joint mechanics throughout the stance phase of walking in adolescents who are obese

Abstract

The incidence of obesity has increased dramatically in children and adolescents, and with this comes health risks typically associated with adult obesity. Among those health consequences are musculoskeletal damage and pain. Previous studies have demonstrated inconsistent effects of increased body mass on movement patterns in adults and children who are obese. The purpose of this study was to investigate frontal and sagittal plane mechanics during walking in adolescents who were obese. Adolescents (12–17 years) who were obese were recruited from a weight management program, and healthy weight peers (matched for age, race and gender) were recruited from the community. Three-dimensional motion analysis of the lower extremities was performed during walking. Analysis of kinematic and kinetic data from 36 adolescents who were obese and healthy weight revealed significant differences in mechanics at all lower extremity joints in both sagittal and frontal planes. Subjects who were obese seemed to use movement strategies that minimized joint moments, especially at the hip and knee during walking. The lower extremity mechanics during walking in the subjects who were obese raise concerns about maintenance of structural integrity of the lower extremity joints over time, given the repeated high stresses across the joints even with walking. Neither the long term consequences of these atypical movement patterns, nor the ability to alter these patterns through therapeutic activities or weight loss has been investigated in adolescents who are obese.

Introduction

Childhood obesity, defined by the Centers for Disease Control and Prevention as having a body mass index (BMI) greater than the 95th percentile for age and gender, has become an epidemic, with 17.4% of all adolescents (12–19 years) in the United States classified as obese [1]. Chronic conditions such as cardiovascular disease and diabetes, commonly seen in adults who are obese, are now seen in adolescents who are obese [2], [3]. Musculoskeletal conditions, including osteoarthritis, low back pain, and soft tissue injury, are often associated with obesity [4], [5]. Increased body mass, with increased forces across weight-bearing joints, has been causally implicated in many of these musculoskeletal conditions [5].

Forces on joint surfaces are increased during any weight-bearing activity, including walking. Increased body mass may increase risk of damage and injury to joint surfaces and other musculoskeletal structures with repetitive loading during weight-bearing activities. Many have hypothesized that movement patterns are significantly different in individuals who are obese. While most studies report that children and adults who are obese walk slower, with a wider step width, shorter steps, and increased double support time/decreased single limb support time [6], [7], [8], [9]. Nantel et al. [10] reported no difference in gait velocity, cadence, stride length or double limb support time in obese versus healthy weight (HW) children.

Reports of kinematic and kinetic characteristics of walking in individuals who are obese are inconsistent. Peak knee flexion angles during stance phase of walking have been reported as being lower in children and adults who are obese [11], [12] while others reported no difference in these angles [8], [9]. Peak plantarflexion angles have been reported as lower [9] and higher [10] in obese versus HW subjects. The lower plantarflexion angles were noted in subjects with significantly slower gait velocity [9]. No differences in sagittal plane hip and knee moments have been found between obese and HW subjects during walking [8], [11], [12]. Compared to HW adults, sagittal plane ankle moments of obese adults have been reported as lower [8] and higher [12] during walking. Nantel et al. [10] reported the only difference in lower extremity sagittal plane kinetics during walking was an earlier shift from hip extension moment to hip flexion moment in obese versus HW children.

Less data is available for frontal plane biomechanics during walking. Compared to HW individuals, peak hip frontal plane angles during stance phase have been reported as significantly more abducted in adults who are obese [9], and as significantly more adducted in children who are obese [13]. The greater hip abduction angles were reported in subjects who walked significantly slower than their lean peers [9]. Greater knee valgus and rearfoot inversion during walking has been reported in children who are obese (compared to HW peers) [13], while studies have alternately reported higher knee adduction moments [13] and knee abduction moments [11] in obese versus HW children.

In summary, a variety of investigations of the effects of obesity on characteristics of walking have yielded inconsistent results. Studies to date have included adults and children (8–13 years old). Frontal and sagittal plane biomechanics in hip, knee and ankle at specific points during the stance phase of walking in adolescents who are obese have not been reported. The purpose of this study was to examine the sagittal and frontal plane lower extremity biomechanics during walking in adolescents who were obese versus HW peers.