I just found this topic and posted one about a mask that I saw.
It's called the Altitude Training Mask www.trainingmask.com
I am finding that many MMA fighters are using these types of masks to conditioning and training. they feel they help the body utilize oxygen better
here is a link to a MMA guy doing a workout with one on: http://youtu.be/v91-ESlGlps
I have thought about trying this myself and see what it does but not sure how people at my gym would think about it!
To the OP cturtle I would ask him about what he is training for! I think he would like to share that information!
I'm a firefighter and I believe this would really help me with my job!ave
Have you seen this guy at the gym since then?