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Effects of speed and grade on the biomechanics and energetics of walking in obese adults

Date

2010

Authors

Ehlen, Kellie Amanda, author
Browning, Raymond, advisor
Reiser, Raoul Frederick, II, committee member
Melby, Christopher L., committee member

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Abstract

Brisk walking is a recommended form of exercise for obese individuals. However, lower extremity joint loads and the associated risk of musculoskeletal injury or pathology increase with walking speed. Walking uphill at a slower speed may offer an alternative form of moderate intensity exercise that reduces joint loading. The purpose of this study was to quantify the biomechanics and energetics of level and uphill walking in obese adults. We hypothesized that compared to brisk level walking, walking slower up a moderate incline would reduce lower extremity joint loading while providing appropriate physiologic stimulus. Twelve obese adult volunteers, age = 27 (5.5) years, mass = 100.5 (15.7) kg, BMI = 33.4 (2.6) kg/m2, (mean (S.D.)), participated in this study. We measured ground reaction forces, three-dimensional lower extremity kinematics and oxygen consumption while subjects walked on a dual-belt force measuring treadmill at several speed (0.50-1.75m/s)/grade (0-9°) combinations. We calculated net muscle moments at the hip, knee and ankle and metabolic rate for each condition. Walking slower uphill significantly reduced net muscle moments at the knee compared to faster level walking (p<0.05). Peak knee extension and adduction moments were reduced by ~19% and 26%, respectively, when subjects walked at 0.75m/s, 6° vs. 1.50m/s, 0°. The greater knee moments during level walking suggests subjects had greater medial compartment knee joint loads. All walking trials were moderate intensity (48.5-59.8% of VO2max). A slower walking speed combined with a moderate incline appears to be an effective strategy for reducing knee joint loads while providing appropriate cardiovascular stimulus in obese adults.

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Department Head: Richard Gay Israel.

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