Adrenaline Sports, what could possibly go right?

While writing this I am waiting for my fiance to jump out of a plane for the thrill, but it makes me wonder are there any possible health benefits from the frightening and exhilirating experience that historically would have killed. My initial thoughts is the obvious that fear and anxiety stimulating the production of norepinephrine and epinephrine with the result of being safe would act as a tool for conditioning through positive reinforcement. Essentially, what doesn't kill you makes you stronger. There is perhaps a deeper cause providing the same result. That being for those who do not routinely stimulate these catecholamines production to such a high level, the sudden influx of hormones which stimulate the autonomic nervous system (fight or flight) would have an overall positive effect on the recipient's sensitivity this hormone. The influx of hormones greater than the capacity of their receptors would give the body reason to generate more receptors. In a sense the body thinks: "If your going to do this all the time I'm going to need more receptors to be ready for the next time you scare me like that." Which in turn means that the next time something happens that makes that person anxious or scared there are more receptors than necessary, so the same amount of adrenaline produces a lesser response.

Other than the psychological aspect of this what else could the very high level of adrenaline cause? We know that adrenaline has an inotropic effect on the heart causing it to beat harder and also faster. The autonomic nervous system pulls blood away from all organ systems apart from the brain and also sends more to the muscles. Could adrenaline sports be a beneficial activity for those with limited cardiovascular endurance? A common cause of atherosclerosis (artery hardening) is sedentarianism. If you don't move and cause an increase in blood flow your arteries cannont increase and decrease in size as well which can lead to clots and ruptures. With such a vasodilatory effect being produced is it in someones best interest to cause such a quick change to their vasculature. As with everything it seems it depends there are many factors need to be considered. The degree of which the arteries can be widen matters since if they are incredibly stiff a sudden cause of dilation could cause a rupture. Similarly, if the blood vessels can dilate and a person is not used to that intensity of vasodilation blood pressure could drop to reducing blood supply to the brain and causing the individual to pass out. It seems that for your cardiovascular health there is benefit to a point after which it could do more damage than good. However, generally it is safe for most.