Static Equilibrium-Friday March 10th, 2017

This week I transitioned from working with the Vicon system, to researching what is actually happening during the lift. This involved looking at two things to start: physics, which I am very familiar with, and excel, which I am not familiar with. Using excel, I had to convert the units for my data, and organize all my data. There are more than 3,600 data points for just one of my lifts. After organizing the data, I transferred it into an analysis program. The analysis program showed us a bunch of information and graphed the analysis for me. We got some puzzling results, so we're still trying to make sure this is accurate. The first graph is the squat lift, the second is the stoop. As you can see, both are very similar and flat. What is puzzling is how flat both graphs are.

After this, I began analyzing my data for just a single frame of the data. This involves assuming a static equilibrium in order to solve for the force and torque at the elbow, shoulder and hip. By assuming a static equilibrium, all the forces and torques must cancel out to equal zero. This is something that I am familiar with doing. One new step that had to be taken was using a proportion to find the approximate weight of arm and wrist, as well as the length. Instead of trying to measure these things by hand, they can be approximated after only knowing the subject's height and weight. For example, take the height of the subject in centimeters and multiple it by (0.146 + 0.108) to find the length from elbow to hand. Because I'm 6'6"(about 198 centimeters) this value was 36.828 centimeters in my calculations. The last thing that must be found is the angle, relative to the horizontal, at the hip, shoulder and elbow. This can be found using the inverse of tangent and the x,y coordinates of the wrist, elbow, and shoulder. By taking the inverse tangent of the difference of the y coordinates, divided by the difference of the x coordinates, the angle can be found. This angle needs to be found in order to solve for torque. Next week, is spring break so I will not be posting, but the week after that, I'll start looking at what this information means, and what to do with it.