Warn about a possible risk.

Adrenalin can be created in many different aspects of life, but in extreme sports, when there is an element of danger as well as the fun of the activity itself, that level of adrenalin is extremely high, and that leads to a natural rush, a feeling of pure bliss

Sometimes extreme sports can be so dangerous if u do it with the wrong gear, for example, the BMX apparently could be a safe extreme sport, but with a great fall or a lack of calcullation you can get a great injury, it could be dangerous.