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Singh B.1, Negatu M.1, Miller M.1, Yack H.J.2
1California State University, Fresno, Fresno, United States, 2University of Iowa, Iowa City, United States
Background: Despite extensive research and continued medical attention, obesity rates continue to rise. Thirty four percent of adults and nearly 20% of the children in United States are considered as obese. Increases in childhood obesity, while certainly emerging from a variety of causes, are clearly related to a lack of physical activity. While empirical clinical observation suggests cardiorespiratory fitness and muscular strength in obese children are important issues that affect participation in activity, underlying biomechanical influences have not been explored.
Purpose: The purpose of the study was to explore the effect of cardiorespiratory fitness, adiposity and muscular strength on walking gait biomechanics in obese children.
Methods: Twenty nine children, 14 girls and 15 boys, mean age 9.8±0.9 years, mean BMI 27.06±3.2 kg/m2 and mean BMI percentile 96.1±4.1, were recruited from University of Iowa Obesity Clinic and Iowa City community. The 15 m Progressive Aerobic Cardiovascular Endurance Run (PACER) protocol was used to estimate cardiorespiratory fitness (V̇O2max). Adiposity measured as percent body fat, was estimated by air displacement plethysmography (Bod Pod). Right lower limb isometric strength was assessed using a custom leg press device.
Intra-red emitting markers were applied to lower limbs, pelvis, and trunk segments to generate subject specific biomechanical anatomical models of walking gait. The subjects walked on an 8 meter force plate walkway while gait kinematics and kinetics were collected using a 3D motion analysis system (Optotrak, Kistler). Peak hip and knee moments normalized to body weight for the right side were analyzed for five walking gait cycles using C-motion software. A Step wise regression model was used to analyze the data. The model included moments as dependent variable and fitness, adiposity and right lower limb strength, as the three independent variables. P-value 0.05 was considered significant.
Results: Mean aerobic fitness as estimated by PACER was low (34.1±6.0 mL·min-1·kg-1). Mean adiposity was 32.2±7.6 % body fat and mean right lower limb strength, was 7.54±2.29 N/kg. The step-wise regression model for hip and knee adductor moments included adiposity as the only predictor variable (adjusted R2=0.3 and 0.22 respectively). Knee extensor moments selected both strength and adiposity as the predictor variables (adjusted R2=0.35) whereas hip extensor moments did not include any variable. None of the step-wise models included cardiorespiratory fitness.
Conclusion(s): The results provide information on how the level of fitness and lower limb strength might affect physical performance during gait evaluations in obese children. Adiposity was the main factor in models for adduction moments, whereas adiposity and knee strength correlated with knee extensor moments. The study suggests that adiposity and strength may have a significant effect on gait biomechanics in obese children, whereas cardiorespiratory fitness did not influence gait biomechanics.
Implications: Adiposity and lower extremity strength most significantly influence an obese childs biomechanical alignment during normal gait activities. The results of this study could make a significant impact for physicians, trainers, and physical therapists as they encourage wellness and fitness among their obese clientele.
Funding acknowledgements: No Funding Source
Topic: Paediatrics
Ethics approval: Ethics approval was provided by Institutional Review Board, University of Iowa, USA.
All authors, affiliations and abstracts have been published as submitted.
