POSITIVE VS. NEGATIVE MUSCLE WORK OF NON-LEVEL WALKING IN LEAN AND OBESE ADULTS.

ECU Author/Contributor (non-ECU co-authors, if there are any, appear on document)

Michael P. McNally (Creator)

Institution

East Carolina University (ECU )

Web Site: http://www.ecu.edu/lib/

Abstract: When walking on non-level surfaces at a constant speed, an individual's total mechanical energy will increase when walking up an incline, and will decrease an equal amount going down a decline. Total muscle work performed however, has been previously shown to be greater during inclined gaits when compared to decline gaits. This can be explained by the fact that during incline gaits muscles will generate energy solely through the contraction of skeletal muscle, and during decline gaits muscles will dissipate energy through both skeletal muscle contraction and other possible mechanisms. One of the proposed mechanisms of energy dissipation during decline gaits is the vibration of soft tissues, which can include muscles, tendons, ligaments, and adipose tissue. The global hypothesis of this study is that skeletal muscles will generate more mechanical energy in gait tasks that raise the center of mass compared to the mechanical energy they dissipate in gait tasks that lower the center of mass, despite equivalent changes in total mechanical energy. Because obese adults have a greater amount of adipose tissue which is available for vibration and dissipation of energy, the sub-hypothesis of this study is that obese individuals will show a larger bias towards net positive muscle work in incline vs. decline walking compared to lean individuals. Healthy lean adults (BMI <25) and healthy obese adults (BMI >35) were tested walking up an incline surface and down a decline surface at 1.5 m/s. Three dimensional kinematics and ground reaction forces were collected and used to calculate joint kinetics through standard biomechanical motion analysis and inverse dynamics. Selected gait variables were analyzed using a two way ANOVA with repeated measures, with p<.05. A significantly greater amount of total muscle work was performed during incline walking compared to decline walking, with obese performing significantly more muscle work overall than lean adults. There was no significant interaction for total muscle work during incline and decline gaits for lean and obese adults. This study is in agreement with the global hypothesis that skeletal muscles generate more mechanical energy during inclined gaits than they dissipate during declined gait, despite equivalent changes in total mechanical energy. The sub-hypothesis was not supported, as obese adults had a similar bias towards total muscle work in inclined gaits. This suggests that other mechanisms may be responsible for the bias towards positive muscle work, including more erect gaits during decline walking, increased positive muscle work from the forward propulsion of the body, or the dissipation of energy through the shoe element.

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Language: English

Date: 1905

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