Falls related injuries among the elderly is a well recognized problem, but little is known about the reasons behind these injuries. The ultimate purpose of my summer research is to find the cause of this problem so that doctors may later be able to treat it.

Subjects: The subjects we used in this experiment consisted of twenty young (under thirty years of age) and twenty elderly (over sixty-five years of age). Ten members of each age group were males and ten were females.

Protocol: A horizontal cable was attached to a padded belt that supported the subject while they kept their bodies in a straight lean position. The cable subject was lowered until a load cell attached to the cable gave a specific reading indicated the percentage of the subject's body weight supported by the load cell. After the subject was in position, the cable was released after a random time delay. In the first set of trials, subjects were instructed to regain their balance any way possible, and in the next set, they were instructed to regain their balance taking only one step. The subjects also wore a safety harness that was attached to the ceiling in order to prevent injury if they could not regain their balance. After the multiple and single step leans, we leaned the subjects at slight angles and instructed them to step a distance one third their height as fast as possible. Finally we had them complete a series of three strength tests to measure their maximum ankle torque, knee torque, and hip torque.

What I did: My first two weeks of the summer were spent setting up the experiment and learning how to use the equipment. The equipment consisted of force plates (which allowed us to measure foot/floor reaction forces and moments), load cells (which allowed us to measure lean angles and harness catches), a step switch (which would send a signal after the subject took his first step), and a trigger (which would release the subject after a random time delay). These four devices were wired up to an amplifier and then into our main computer. Our main computer was also connected to an optotrak camera which could measure the positions of 16 infrared markers placed on the subject. The next five weeks were spent testing. I spent most of this time either running a computer or leaning the subject. Since I was the first to learn the equipment, I also spent a lot of time teaching others how to run the experiment. Occasionally, when I was not needed in the lab, I went to the computer and analyzed data. The final three weeks I spent continuing to analyze data and creating a multimedia video of our experiment. I concentrated most of my efforts analyzing the strength data. The important trend I noticed was that although the young were only slightly stronger than the elderly, they could generate torque at a much greater speed.