cant do cardio for more than a few hours without pain

OK didn't know here else to post this, is kinda related to fat loss, as it's impeding it, heh.

I'm 27 years old. Ive been weight training since 18, with a few on and off periods. I have a nagging pain in my lower back and occasionally shoulders. But don't have anything serious enough for a doctor to have taken seriously (certainly not a sharp pain) I'm trying to lose weight fast. I'm at a pretty big calorie deficit, but I really don't care if i lose some muscle too, I am sick of being flabby nowadays.

I'm weight training 3 days a week (not pushing too hard) and doing an hour of pretty hard running on the treadmill another 3 days a week.
Yeah that's fine.

However I'm pushing myself a bit more than that. after either the weights or the running, I try to do another 3 hours of gentle cardio (I have audiobooks, I figure I may as well read it whilst exercising rather than sat down) I either go on the treadmill or the elliptical cross trainer thingy. If i walk more than an hour, I start getting a very annoying dull ache in my hips.. and the cross trainer hurts my lower to mid back for a day.

This is only additional GENTLE exercise though, I am only 27. Is this normal? How the hell do people train for marathons? I heard of swimemrs doing many hours a day etc.
Am I just injured, or just getting old? Thanks.

While I'm sure you would eventually get used to walking for 3 hours, why the hell would you want to. You already run 3x a week...

Isn't it obvious, suppose not otherwise you wouldn't be asking.

You are doing high impact cardio with a back injury, and 3 to 4 hours a day.

cardio for a few.... hours?

[QUOTE=lee__d;1019274443]While I'm sure you would eventually get used to walking for 3 hours, why the hell would you want to. You already run 3x a week...[/QUOTE]

i just want to burn a few extra calories a week, id be sat down listening to the book anyway.

askie
You are doing high impact cardio with a back injury, and 3 to 4 hours a day.

its low impact for that period. high impact 3x1 hours a week.

You should make the weight training your top priority and cut out some of the cardio. If you want to lose fat adjust your diet accordingly. 3 hours of cardio a day is ludicrous...