I would rather die of autoerotic asphyxiation and my mother find my body, hanging, pants down and penis in hand with porn playing on my mobile phone, than be found training in one of these masks.
Would be a great honor to smell one of Markus's farts.
Bahahaha, I'm never gonna let you off this one man. OMG you're one of them huh?POuahahahahaha......
For most movements sure. But runners and other athletes can find value. http://naturalrunningcenter.com/2013/10/20/breathing-exercises-runners/Lots of ways to learn to breathe better. For some the restrictive mask helps by making them more conscious of their breath.
I`ve got 3 of them hanging on my seldom used treadmill out in the garage.