It can accelerate hairloss, if you work out hard.
Why? Because when you work out very hard, you stimulate the growth hormone and that generates more Testosterone, which means more DHT.
I worked out in the past and I noticed increased hairloss (when i was not in any treatment)
Now, I'm about to start working out again, but I will take it easy.
Also, what helps a lot is running and aerobics. That is very good for hair, because you keep healthy and you reduce your fat levels, which is good for hair.
Also, be sure to be into a good diet.
If you are into a good diet, you do enough cardio and you work out with a moderately good rutine (not like Ronnie Coleman
), you won't have any problems.
Good luck.