Help! I have just gone up to running 3 mins and walking 30 secs. I have tried it twice now and can't finish it. The first time I finished the third interval and then experienced crampy type pain on the inside of my right calf with a small amount of swelling. I rested and the pain was completely gone after 3 days. I tried the run again but a lot slower but this time I only managed 2 intervals before the pain returned. It wasn't as intense as before but I walked the rest of the run. I am so disappointed as my cardio ability has really improved but I am being let down by my legs. How can I get past this?