I think the issue here is whether you began racing (and continued to race) until now. If you were fit and fast at 20 you will probably start to slow down a bit in you 40's.

That is a BIG generalization. You will probably lose some of your sprint and have to change your training to factor in a bit more recover time but you can still be pretty fast well into your 40's. I'm almost 45 and, at 44, was routinely racing and besting guys half my age.

For those few we can point to who are even older than that and still really fast that's just genetics. Not much you can do about that.

The good news is that there is an increasing amount of information, clinical studies and good coaching being thrown at Masters racers. The information is out there so that you will be able to maximize whatever potential you have.

In the end, as Pcaddy points out, you'll never be a pro so just train hard, eat right, recover smart, race yer arse off and enjoy the hell out of it.

Go old farts!