Thranhardt finalist questions energy flow in ankle push-off

CHICAGO — The role of ankle push-off in human walking has been a controversial issue, Liang-Wey Chang, PhD, CO, PE, said during his Thranhardt presentation at the American Academy of Orthotists and Prosthetists Annual Meeting and Scientific Symposium.

“Studies on the role of ankle push-off in human walking have not reached a unified conclusion,” he said.

The term “push-off” in literature means the power source for propulsion, he said, but previous studies did not suggest where the push-off energy goes. However, many push-off products have been developed in the O&P, such as feet and other energy-returning devices.


Liang-Wey Chang

“But do we really know how the human push-off energy is used before designing and fitting these energy returning devices?” Chang, who is an associate professor at the Institute of Biomedical Engineering, National Taiwan University, said, here.

He presented a novel, symbolic model to depict energy flow among the ankle, knee and hip joints.

“Our objective was to study the ankle-push-off  function in view of the effect of ankle push-off power to tell where the push-off energy goes,” Chang said. “An energy flow model of human gait was developed to analyze the utilization of ankle push-off power comprehensively and intuitively. We hypothesized the ankle push-off power would be a power source for preparing the following swing of lower limb segments but not for pushing the trunk forward.”

Chang’s colleague, Hung-Bin Chen, MS, presented study data in which researchers used infrared motion capture to analyze 10 able-bodied participants who walked with shoes at self-selected speeds.

Using their symbolic model of energy flow, Chen showed peak ankle power generation, which he said should be the most representative instant for ankle push-off. Further, the model illustrated their hypothesis, Chen said.

“In the energy flow originating from the ankle, or ankle push-off, we can see that part of the ankle power downflows to the ground and another part upflows to the thigh but does not go beyond. The ankle power does not go up to push the body. The beauty of the energy flow diagram is to graphically reveal the specific movement strategy in the systematic view, rather than focusing on a single joint or segments.”

For more information:

Chang A. Paper TL3. Presented at: American Academy of Orthotists and Prosthetists Annual Meeting and Scientific Symposium. Feb. 26-March 1, 2014. Chicago.

Disclosures: Chang and Chen had no financial disclosures.


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