Accepted for Publication: Soft tissue deformations contribute to the mechanics of walking in obese adults
Our research article was recently accepted for publication in the journal of Medicine & Science in Sports & Exercise (MSSE). This work was performed in collaboration with researchers from the University of Michigan (Fu & Kuo in the Department of Mechanical Engineering) and from Colorado State University (Board & Browning in Department of Health & Exercise Science).
ABSTRACT
Obesity not only adds to the mass that must be carried during walking, but also changes the body’s composition. Although extra mass causes roughly proportional increases in musculoskeletal loading, less well understood is the effect of adipose tissue, which is relatively soft and mechanically compliant. Purpose: To estimate the work performed by soft tissue deformations during walking. The soft tissue would be expected to experience damped oscillations, particularly from high force transients following heel strike, and could potentially change the mechanical work demands for walking, in amounts thus far unknown. Method: We analyzed treadmill walking data at 1.25 m/s for 11 obese (BMI > 30 kg/m2) and 9 (BMI < 30 kg/m2) non-obese adults. The soft tissue work was quantified with a method that compares the work performed by lower extremity joints as derived using assumptions of rigid body segments, with that estimated without rigid body assumptions. Results: Relative to body mass, obese and non-obese individuals perform similar amounts of mechanical work. But negative work performed by soft tissues was significantly greater in obese individuals (P = 0.0146), equivalent to about 0.36 J/kg vs. 0.27 J/kg in non-obese individuals. The negative (dissipative) work by soft tissues occurred mainly after heel strike, and for obese individuals was comparable in magnitude to the total negative work from all of the joints combined (0.34 J/kg vs. 0.33 J/kg for obese and non-obese adults, respectively). Although the joints performed a relatively similar amount of work overall, obese individuals performed less negative work actively at the knee. Conclusion: The greater proportion of soft tissues in obese individuals results in substantial changes in the amount, location, and timing of work, and may also impact metabolic energy expenditure during walking.
Fu, X. Y., Zelik, K. E., Board, W. J., Browning, R. C. and Kuo, A.D. Soft tissue deformations contribute to the mechanics of walking in obese adults. MSSE. In Press.