What I am surprised about though, is that in the last 4 days I have noticed my thighs are starting to grow. This may be temporary but I find often that when I do a lot of sport and the distances are not really large, I tend to bulk up. If I want to stop my thighs from growing even more I will probably have to start running longer distances again. I think once you get to a certain distance your body realises it is inefficient to have large bulky muscles and starts converting them to lighter wiry ones instead. It will be good if this happens as there will be a lot of hills to climb in South America, and power to weight ratio rather than raw strength is what counts.