I did my second run today in week 1 at the gym on the tred mill. I must say that I found this a lot easier than running round the local field so I feel like a bit of a fraud this time. The experience was so different to the first run.
I took the advice from you all and slowed down so the breathing was easier and the chest didn't hurt!
The next run will be back at the field so that will be the test I suppose. As a new runner would the difference be that noticeable between gym and outdoor?