Any biomechanics people here - help needed

Underground
1

  I was wondering if you could help me out. I need help on how to calculate joint reaction forces, ground reaction force and torques.



Basically I'm doing a mini project on runners with a forefoot strike vs. heel strike for my biomechanics class. I have two pictures of the same runner one doing a heel strike, and one doing a foot strike. I've made free body diagrams of them, (two link models, separating the foot and the lower leg).



And I have an anthropometric table, so that I can measure the segments and use the table to figure out the Center of Mass for the segment.



I guess I'm just not getting where the angles come into play . And I have to put in my own numbers/data cause there is none available. So I am gonna go by the assumption that this runner is 150 lbs.





Here are the pictures:



Heel Strike







Forefoot Strike



2

You need to post free body diagrams with at least velocities.

Then I can figure out if I even remember enough physics to help you.

One thing to consider is that the forefoot strike has more of a roll to it, as opposed the heel strike which is more a true strike with much higher registries on force plates.

Here is a video of the study conducted at Harvard

http://bcove.me/0idl250j

3

After looking at the video, you definitely need the descending velocity vector of the foot to be able to calculate forces and torques.