Well basically over the past two months with my training my fitness has been shooting up, from just being able to run 3 miles i was soon smashing 10 milers following a marathon training programme. However last weekend i went away for an induction with the RMR so i rested the week before it and have rested this week aswell as my muscles were killing from the weekend. I thought I could just carry on training as normal as i had a good gym session yesterday and so went on to do a 12 mile run tonight but within a mile my legs and knees were killing and i was really struggling to breathe, not only did i not complete my 12 miles i only did 4 miles in a shameful 40 minutes, I dont know if it was just a bad day or not but it got to the point where i couldnt actually breathe and it felt like someone had been punching my lungs and it killed! Has this happened to anyone before? did it happen again or is this just a one off?