What the heck is Marshawn Lynch wearing in warmups?

[KitsapGuy]

:16: :229031_confused2: unno:

[youtube]DYNwAQUplec[/youtube]

 

[dontbelikethat]

Looks like an oxygen mask.

 

[bandiger]

Elevation Training Mask

 

[kmedic]

Lol, does anybody know what it is? I assume it's something to improve performance.

 

[pmedic920]

http://www.trainingmask.com/about-eleva ... ning-mask/