Why does your heart rate remain very elevated after heavy exercise?


a) normal sinus rytham is concidered to be normal anywhere between 80-100 for adults but the fitter you are the lower that is and even HR's lower than 80 (sinus bradicardia) are normal for a lot of quite fit people

b) the parasympathetic nervious system isnt like the sympathetic (ie VERY rapid onset), it takes a long time for it to regain dominance after sympathetic activation. Adrenilin as a drug for instance has a half life of 20-30 min after admistration IV so you can see that it will take a while for that to get out of your system. Actually a good example is vagal nerve (parasympathetic) stimulation (caroted massarge) for tachicardia. Its effects arnt seen for a good 15-20 min at least

c) stimulants on top of excersise can be quite dangerious. You risk the heart going into failure because its being told to do to much. If your excersising your ALREADY pumping adrenilin which binds to the alpha and beta 1 receptors and causes an increase in HR and contractability. Add caffinee on top of that...

d) fluid replacement is important, symple as that. So is salt replacement which can have effects on the heart, especially calcium and potassium highs and lows
I'm 18 years old though, isn't 96 around normal?
It's not exactly abnormal but it's closer to the typical range for women. If you work out regularly it should be lower. Doesn't leave you much room to elevate as you grow older. It doesn't usually get lower unless you start out as a slug and one day decide to get in shape.
I don't know my blood pressure but it seems to be low, I have very frequent head rushes from standing.
Why don't you just measure it and stop guessing? These days there's a free blood pressure meter in a shop somewhere on every block, they've become so small and cheap. The biggest supermarket chain (Giant) has them here in Washington. The nurse's office at school or the occupational health office where you work probably has one.

If you get head rushes just from standing up it's about time you take that body to a doctor. You've got symptoms you shouldn't have for another forty or fifty years.

Of course we've all told you the same things a doctor will tell you. Start taking better care of your body if you want it to last a lifetime.
Low BP (subjectivly measured by pain or fainting on standing) with a high HR is not really a good sign. As far as the formular for measuring BP states that it either means that your body is not constricting the perefral capillary bed as it should (big bucket syndrom relitive shock), that the kidneys arnt maintaining enough blood volume (apsolute shock) or that cardiac contractability is compromised
oh BTW you can check perfusion (which after all is the end game of BP) without anything except you finger. Just press a finger untill it goes white and then let go, the colour should come back in less than 2 seconds, any longer than that and perfusion is compromised and there is a problem:)
I just did that perfusion check thing. It comes back in about half a second.

@Fraggle, I do work out regularly but don't do much endurance training. I mostly just lift weights, I only recently started running.