In this Sports Illustrated post Daniel Friedman discusses the interesting mask Marshawn Lynch is wearing in the picture above.
It was recommended to him by a friend. He uses it to train as it makes it more difficult to breathe and increases his lung capacity. For the full story click the link below:
(continue reading at: http://www.si.com/edge/2015/01/26/marshawn-lynch-training-mask-seattle-seahawks )