A new model developed by researchers at the Ohio State University will be able to tell us how toe strength can determine how far people can lean while keeping their balance.
The model could lead to development of robotic body parts that will closely imitate human movement, and might lead to a new generation of advanced prosthetics.
"In order to reduce the complexity of the problem, the feet are often either neglected or modeled using simple shapes that don't really give full credit to the importance of feet," said Hooshang Hemami.
Hemami and a colleague, Laura Humphrey, designed a computer model of a body and foot which assigned four different sections to represent different parts of the foot, while assigning the body one section. This allowed Hemami and Humphrey to focus primarily on the pressure of the feet and toes as they manipulated the forward motion of the body.
The researchers performed simulations of static balance and forward leaning in the computer-modeled body, and compared the results to those observed in the scientific literature.
The computer model can perform forward leaning indefinitely, but human subjects will experience muscle fatigue eventually, explained Hemami.
The team conducted tests for three different cases: static balance in healthy subjects, static balance in subjects with diminished toe strength, and forward leaning in healthy subjects.
Results indicated that in a healthy person, toes became increasingly important as the person leans forward.
As the computer-modeled body leaned forward, the pressure underneath the toes increased significantly, and the pressure underneath the heel decreased in a similar fashion.
When the same tests of static balance were performed on the computer-modeled body with diminished toe strength, the pressure underneath the toes remained at zero.
The maximum angle that a healthy computer-modeled body could lean forward from the waist without its heels lifting off the ground was nearly 12 degrees from vertical. The model with diminished toe strength could only lean forward nearly 10 degrees.
One discrepancy: his computer model was able to lean forward 12 degrees without lifting its heels, while real people were only able to lean two-thirds as much -- 8 degrees.
"This discrepancy could be psychological - that people do not feel comfortable using their maximum theoretical range of motion," said Hemami.
"Now that we have a reasonable computer model, we hope to explore, in the future, the sensory apparatus and other functions of the toes in diverse human activities," Hemami said.
In the future, Hemami wants to model the human spinal cord and develop a mathematical system that can determine the level of reaching and pushing required for certain tasks.
"My hope is that my work will inspire construction of robotic models of various body parts that can move similarly to the human body. If you can make a robot or computer model kick a soccer ball like a soccer player, we will have a better understanding of how various parts of the body work during movement. Then, perhaps, you can build an artificial spinal cord that could help the handicapped," Hemami said.
"Attaching a robotic spinal cord to the outside of someone who is handicapped could help muscle development."
"We try to model what muscles do, which may help to develop more advanced prosthetics, so we have something better to offer people who need them," Hemami explained.
Their work was published in a recent issue of the Journal of Biomechanics.