If you reduce oxygen you are increasing your body's need to work anaerobically - which it does - as it builds up lactic acid. Swimming is probably just as good in developing the same or better breathing benefits
well maybe thats the idea - if he is running faster than his aerobic threshold (which for a pro league guy like him could be 15kmph) he will be in anaerobic zone even without a mask. the mask might be to force into anaerobic zone at a lower speed or ++ the work post his natural threshold. the position of his back leg on the side photo indicates he is running very fast like 20kmph. he is doing interval training not a prolonged run....routine for sprinters and middle distance athletes. even marathoners do it for strength and finishing speed.
while he can handle this, I would agree that most of us cannot. btw amitabh bacchan wore it in a movie Pink recently.
One of the changes of high altitude training is an increase in the red blood cell count, mediated by a natural body chemical called Erythropoietin. Injections of that stuff would mimic that effect. India manufactures the stuff by the way. Look out for huge orders from China
it comes in little red pre-loaded syringes right? i used to buy them for my late father. his kidneys had failed, which somehow affects the bone marrows production of RBC, which made his blood counts low , hence the periodic injections.
i think EPO is used by athletes and cyclists to blood dope also.