Last month I added one of these to the repertoire and am currently using for my own training to test it out. It’s called an Elevation Training Mask and it mimics the effects of high altitude training by creating varied resistance to your breathing whilst training.
The concept behind it? When elite athletes want to improve their performance they go to high altitude levels to train. When they come back to sea level they perform much stronger, faster, and have increased endurance. So far I have been seen an increase in my caloric burn to around double the usual rate during a mixed resistance/light cardio session and a severe drop in my endurance whilst wearing the mask.
For more information from the source, click on their Australian site HERE