The model that Hemami and Humphrey built allowed them to produce results that supported the findings of balance shown in real subjects. They 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.
In order to have the model mimic a subject with diminished toe strength, Hemami and Humphrey weakened one of the sections in the computer-modeled foot, which represented a muscle located just above the big toe. This muscle helps control the foot's arch, which provides support to the body while standing.
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. Initially, the pressure underneath the heel was significantly higher than in the healthy subject, and as the body leaned forward, the pressure underneath the heel only decreased by half the amount that it did in the healthy subject.
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.
The computer model supports past studies on real people, Hemami explained. 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
|Contact: Hooshang Hemami|
Ohio State University