Childhood obesity differentiates lower extremities’ biomechanics during gait

Introduction

Worldwide childhood obesity has increased by 50% in the past 30 years (Smith et al. 2014). Numerous studies suggest that overweight and obese children have subsequently developed short- and long-term health problems that follow them into their adult life (Cruz et al. 2005, Kiess et al. 2001, Puder & Munsch 2010, Taylor et al. 2006). Particular, psychological co-morbidities associated with being overweight or obese during childhood and adolescence are well documented. Obesity in children is a significant public health problem, and it has the potential to have an impact on a child's osteoarticular health, resulting in ongoing chronic pain. An increased body mass is reported to have negative influences on many manifestations of daily life such as control of postural stability, any kind of locomotion but with the most crucial that of walking (Cimolin et al. 2014, Galli et al. 2000, Hills & Parker 1991, Sibella et al. 2003).

Walking is the most popular form of physical activity for weight management. Biomechanical studies in this field are critical. McGraw et al. (McGraw et al. 2000) demonstrated that overweight boys present a greater double stance phase during gait compared to normal-weight counterparts. In a similar study (McMillan et al. 2010), were found significant differences between over-weight and normal-weight adolescents at lower limb joint kinematics and in their gait strategy. In fact, over-weight children adopt a gait strategy that requires greater dynamic balance (Shultz et al. 2010) by increasing their base of support and time spent in ground contact as previous already stated (McMillan et al. 2010, Nantel et al. 2006). In addition to this, relevant research revealed that overweight children present an upright position while walking through reduced knee flexion and ankle dorsiflexion in swing phase of gait (Gushue et al. 2005).

Little research exists to examine and compare the kinematic and kinetics variables of overweight and normal-weight children on lower extremity joints. Thus, the present study was conducted to determine the impact of excessive body weight on gait biomechanics in overweight and normal weight children during steady treadmill walking. Our hypothesis was that obesity in children modifies the kinematic and spatiotemporal parameters during gait.

Material & methods

Participants

Ten overweight children boys and 10 individuals of normal weight participated in this study. Body mass index (BMI) was used in order to classify children according to the Centers for Disease Control and Prevention growth charts for age and sex (Kuczmarski et al. 2000). Overweight children had a BMI greater than the 95th percentile whereas normal-weight ones had a BMI less than the 75th percentile. Only male subjects were studied to eliminate possible gender differences in postural stability and gait characteristics. Group anthropometric characteristics are presented in Table 1. All participants were free of any neurological deficit that could influence the lower-extremity performance and they did not have any back or lower extremity injury history. Before testing, parents of all children read and signed a written informed consent statement.

Procedure/Test protocol

Gait was performed on a horizontal treadmill set at 1.2 m/s, graded at 0% (Technogym, Italy). This velocity is found to be comfortable for all participants and adopted due to previous relevant study (Paschalis et al. 2007). Kinematic data of joints were obtained from the VICON 612 Motion Measurement and Analysis. This optoelectronic system consisted of six video cameras, sampling at 100 Hz, and a computer system for data acquisition, processing and analysis in a three-dimensional level. Sixteen reflective markers (14 mm spheres) were placed at anatomical bony landmarks of each lower extremity [posterior superior iliac spine, anterior superior iliac spine, lateral thigh, femoral epicondyle, lateral tibia, lateral malleolus, calcaneus, 5th metatarsal head, and the dorsum of the foot, fig.1] (Davis 1991). The static and dynamic calibration for the motion analysis system was assessed by the same investigator according to the manufacturer recommendations before each data collection session. The experimental model idealized the lower extremity as a system of rigid links with spherical joints. These joints were assumed to have a fixed axis of rotation. All participants were asked to walk at a steady speed for 30 seconds. During this period, sagittal plane joint kinematics were collected. Five right-sided trials at the final 10 seconds of walking steps of every participant were accepted for analysis when their right foot was completely on the treadmill. The average of the five trials was then calculated. Trajectories were filtered with the generalized cross validated splines (Woltring 1986). Prior to the kinematic evaluation, each participant was asked for recording in a standing position onto the treadmill, position which then was used as reference for joint movement. Averaged curves, normalized to 100% of gait cycle, were calculated for the joint kinematics for each participant at the same speed. Hip, knee and ankle joint values in specific gait cycle instants were assessed in the sagittal plane as above-mentioned. Kinematic patterns were normalized to percentage stance duration, where 0% was heel strike and 100% was the toe-off.

Statistical analysis

Independent samples t tests were used to determine whether the mean anthropometric data values, spatiotemporal parameters and kinematics of lower extremities of the two groups (overweight and normal weight children) differed significantly. All statistical analyses were performed using SPSS 15.0. with a significance level set at p<.05.

Picture 1. Marker set-up for the motion analysis data collections in a child participant

Results

No significant differences in age or height were found between the overweight group and the normal-weight group. On the contrary, the mean values of body mass and BMI for the overweight group were significantly greater compared to those of normal-weight group. (Table 1).

Overweight children presented higher stance duration compared to normal-weight children (p<0.05). As well as that, it was found that single support phase duration was statistically shorter in the overweight children group compared with the normal-weight children (p<0.05). In addition to this, step length was almost the same between the two groups. Finally, width step was larger in overweight children compared to normal-weight individuals [(p<0.05), Table 2].

Regarding kinematics, analysis revealed significant results. Beginning with hip joint, it was found that overweight children and normal weight individuals exhibited almost the same values in overall flexion-extension movement but not the same during initial contact (p<0.05). The same was not found in the knee joint as overweight children found to flex less their knee joint during stance phase compared to normal-weight children (p<0.05). Finally, regarding ankle joint during gait, it was shown that obese children presented higher ROM in this joint during overall phase compared to their normal-weight counterparts [(p<0.05), Table 2]

Table 1. Descriptive statistics (mean ± SD) of Over-weight and Normal-Weight participants
Group	Age (years)	Mass (kg)	Height (m)	BMI (kg/m2)	BMI Percentile
Normal-weight	10.9 ± 1.4	38.9 ± 7.4	1.46 ± 0.3	18.2 ± 1.8	55th
Over-weight	10.5 ± 1.3	59.0 ± 8.8*	1.51 ± 0.2	27.8 ± 3.0*	95th
Data are given as mean (±SD) *Significant differences between groups (p≤0.05)

Table 2. Joint Kinematics of lower extremities and spatiotemporal parameters of Over-weight and Normal-Weight participants
Parameter	Normal-weight		Over-weight	significance
Spatiotemporal parameters
Stance (%Gait Cycle)	57.3 ± 2.7	62.5 ± 2.8			*
Single Support (%Gait Cycle)	38.5 ± 2.0	34.1± 2.9			*
Double Support (%Gait Cycle)	18.8 ± 4.2	28.4 ± 5.3			*
Step Length (mm)	0.59 ± 0.06	0.63 ± 0.06			ns
Step Width (mm)	0.74 ± 0.13	0.98 ± 0.25			*
Kinematic parameters
Hip at initial contact (°)	28.8 ± 7.0	42.6 ± 9.5			*
Knee at initial contact (°)	4.7 ± 4.2	0.9 ± 3.5			*
Ankle at initial contact (°)	-1.2 ± 2.1	-4.4 ± 2.2			*
Hip range of motion (°)	41.8 ± 9.6	40.5 ± 7.2			ns
Knee range of motion (°)	58.8 ± 9.6	53.4 ± 8.5			*
Ankle range of motion (°)	22.0 ± 5.5	29.8 ± 6.2			*
Data are given as mean (±SD) *Significant differences between groups (p≤0.05)

Discussion

In our study, significant differences were found in the gait pattern of overweight boys when compared with normal weight individuals. Regarding single support phase, our results are in agreement with relevant studies which revealed that normal-weight children elongated this phase compared to overweight children group (Hills & Parker 1991, Nantel et al. 2006, Spyropoulos et al. 1991). Continuing, over-weight children adopt a gait strategy that requires greater dynamic balance by increasing the time spent in ground contact (double support phase) and increasing their width step and this finding is in agreement with previous studies (Blakemore et al. 2013, Deforche et al. 2009, McMillan et al. 2010, Nantel et al. 2006, Shultz et al. 2010). In combination with the fact that overweight children spent more time in double stance phase compared to normal weight group, this could be attributed to stability purposes during stance phase as obese children probably feel more balanced and adapted different strategy for better stability (Nantel et al. 2006, Winter 1980).

As for the less knee flexion that overweight children revealed, this finding comes in accordance with previous research (Cimolin et al. 2014, Gushue et al. 2005, Hills & Parker 1991, McMillan et al. 2010). They probably flex less their knees to compensate for relative knee extensor weakness or as compensation for instability within the knee structure. This was accompanied with an increment in hip flexion in order to produce toe clearance and limb advancement as occurred (Shultz et al. 2009)

Conclusions

Over-weight children seemed to alter their gait strategy probably in order to avoid an increase in the mechanical work required to move their excess body mass. However, the main limitation of this study is the relative small sample size and the fact that they were not enrolled in the study female obese children. Our findings could therefore not be generalized to both genders. Further additional studies on female participants will be needed to clarify the plausible sex related differences of the examined parameters during gait.

Acknowledgements

The authors wish to acknowledge that grant was supported by the Aristotle University of Thessaloniki (scholarship from AUTH Research Committee, Greece).

Conflicts of interest - There are no conflicts of interest

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