During the last few months I have started to suffer persistently suffer from a calf strain in my right leg about 20 minutes into any run I attempt . I have a good pair of running shoes, always stretch and warm up first and have tried flat softish ground as well. I find that I can swim, cycle, use the rotex cross-trainer in the gym and complete all day long hikes on the moors with no problems at all. I am waiting to see an NHS physio and if that proves a long wait I might have to go private. Before I do this I would be grateful if anyone could shed any light on what be happening or any strategies I could employ to get over this frustrating injury. I have run for over 30 years and have not had this sort of injury before.