I'm Female, 45 years old and 5' 6" tall. Up until recently I weighed 110kg (around 248lbs) and am now down to 87.3kg (192lbs) so it's a 50lb weight loss to start with all from walking 5+ miles a day. I fractured a kneecap 15+ years ago and I used that as an excuse not to do things but in hindsight it was more likely the 110kg that was holding me back. Anyway... when I started to lose weight I said to myself that I would start running when I hit 80kg. Last weekend I had a bit of a think about it and started wondering if I really did need to wait until I was down to 80kg. The way I am going that would be another 2-3 months away.
Monday morning I went out for my first c25k run and I felt fine. My knee didnt hurt. I wasnt hugely out of breathe and I got through the entire experience relatively easily. Certainly more easily than I thought I would. To say I was happy about it would be an understatement. Here are the "run" details: http://www.rundouble.com/?page=map/3141039/RVEGgG2735
So today I went out and did Week One Day Two and I totally struggled. I only managed to do 6 intervals rather than 8. I couldnt breathe. My legs felt like jelly. It was awful. I ended up walking from the end of R6 because I could barely get a breath. I dont think I pushed it at the beginning at all so I dont think that is it. I cant believe that I struggled that much. Here's the details of W1D2: http://www.rundouble.com/?page=map/3072014/YrSFCaNCrk
I dont think I did anything different between the days that should have made me be like that.
Any hints, tips, thoughts, comments would be most welcome because I dont understand why it was SO different from one day to the next. I dont intend to give up as I really want to do this but I want to try and understand why this happened.
Any number of things. Maybe you weren't quite fully recovered from D1. Maybe it was anticipation, or other things in your life that affected your mood. Maybe you didn't sleep well last night. Maybe you went at a different time of day, or ate differently or earlier or later. Which is not to say that you should obsess about any of these things. Only that there are many possible explanations and not to worry too much. Maybe repeat the day, maybe change some things if you think they may have had an affect. Lots of things can affect your run. Over time you will figure out many of them and adjust for them or allow for them. For instance, if the run is not going well, you may realize "No wonder, I tossed and turned all night."
So all that said, last resort is "There will be bad days!" As well as very good days. Guaranteed.