I was just out training today and I was just messing around trying to figure out ways of running more relaxed. The thing is that I have a very big stride and a lot of people praise me for it. I tried breaking my stide down and the result was amazing! this is 100% true. I ran 65 seconds for 400s off 45 seconds rest then on the 4th one I ran 63s for the whole session which was 18! I'm so happy and I'm shocked that this was in actual fact my disadvantage. I was probably using all my energy before with stride length. what do you people think?