Reiterating what's already been said. I thought I'd get out there and start jogging my first time too. BWAHAHAHAHAHAHAHAHA Well, actually...I did. I jogged. Went about 15 feet and felt like my heart was going to explode out of my chest. ::sigh:: So I quickly figured that I couldn't just go out and jog. I started walking instead. And then I'd try a short 10 or 15 ft. jog, then walk and jog, and so on. Eventually, I'd jog more than 15 feet. Then I jogged 1/4 mile, then a half. Then I upped my distance to 2 miles and kept walking/jogging. Soon I jogged a full mile and walked the other mile. Eventually, I jogged 3 miles straight. Then I worked on speed and got settled in at three 10 minute miles each day.
Here's the kicker. I then went indoors for the winter and jogged on a treadmill. BWAHAHAHAHAHA Suddenly, I wondered what happened to my 3 miles. It was a totally different workout. I was still jogging, but now on a machine instead of on pavement. It made a difference. So I had to work up to 3 again. This time of course it went much quicker because I was in better shape.
Next...I hit the elliptical. I felt like I was gonna die early on into that workout. Totally different muscle useage, different workout, and my body had to again adjust. Before summer came along again, I was doing 1 hour elliptical and 30 minutes jogging on the treadmill each day, followed up by some stretching and weights.
I'm just getting back into jogging after pregnancy and getting adjusted to being a mom again. Been back into jogging nearly daily now for over a month. And I'm only up to 2 miles. Then again, it's once again different. Now I'm jogging pushing a stroller. It again makes for a difference in the workout. But I'll adjust and be doing my 3 miles again soon enough. It just takes time.