Interesting that you bring that up.
Most gamers (like CS:GO, DOTA 2, Starcraft II, and even LoL) have to keep pressure and energize themselves constantly, such as normal exercise, eating the right stuff, etc.
They still have to wear these special gloves and drink energy drinks in order to execute the right orders.
It is studied that most gamers need to keep a very constant and high heart rate (I believe about 150 BPS [beats per second]) to make 360 actions per minute.
This is 6 actions a second, which is why you see 'un-Godly' reactions in most cases, because they slightest thing they see will cause one of 6 actions in that second.
If the heartrate wasn't so high, reaction times will be a ton slower, and not have such incredible strategy execution and swiftness (swiftness, if you saw SSW in World Championship's final, is key to executing a good game in a short amount of time before the enemy reacts).
Basically this: They keep a healthy blood pressure to keep a fast heartrate which helps them react much faster to situations ingame.
