Monday, May 13, 2013

J visits the gait lab

My poor baby, J, was sick for his fourth birthday last week. It started the day before his bday party and lasted through the weekend until Wednesday of last week. Wednesday, he was still banned from school but feeling good enough to be compliant while I got some work done at the office. For fun, I thought I'd show him what I do.

I manage a motion capture laboratory where we use special cameras to analyze the forces and moments on knees through gait analysis. Gait is a fancy term for walking. Ultimately, we want to find out where knee osteoarthritis starts before symptoms appear in order to develop interventions to slow or even prevent the progression of osteoarthritis (the degeneration of the cartilage - that slippery material that helps your knee move without friction/creaking). Currently, osteoarthritis is diagnosed once you feel pain, and you can only treat the symptoms.

Well, my little guy doesn't know the particulars of my job except that I have access to some cool science equipment. We decided to do a quick collection with J. We stuck reflective markers on our subject. The markers are plastic balls covered in reflective material, like what's on running shoes. The special cameras then send out infrared light to detect the x, y, z position of each marker during each frame of the collection period (typically 120 capture points/second - aka 120 Hz sampling rate). We have force plates (sensors) embedded in the floor too.

J with the motion capture markers

J insisted on the forehead marker

Then instead of walking, I had him dance around. Here's what was reconstructed in the computer (looped twice). The red arrow is the force J is exerting on the floor.

John just showed it to him for the first time, and J was able to point out his feet, legs, and arms. He loved it.

Then just a fun picture of J and the floor plunger (technical term "floor panel lifter"). It's just not working:

I actually got work done too! Win win!


  1. He looks so excited to be at your lab! I remember seeing a video about a motion tracking system like this used in making Monster, Inc. at Pixar!

    1. Yes, we use the same technology that they use in the movies and video games. It's very exciting stuff :-)

  2. I want to see him lift himself up with the floor panel lifter.... Unfortunately that would not be science.

    1. You are correct, it would be magic since it's not going anywhere :-)