Run 1 of W7. Got through to 24 minutes running (well, jogging), when Laura (bless her) says something along the lines of "Well done, only 60 seconds to go. If you feel ok, why not up your speed a bit.". 'O.K.' thinks I. So lengthens my stride, ups the speed and feeling very proud of myself, as THIS feels like real running. Then about 30 seconds in 'TWANG' goes the muscle in my (L) calf. Carried on in a compromised way and finished the run. Rested up for two days. Did R2 on Sunday, Slight soreness, but there was a triathlon going on in the park where I run, so that took my mind off the soreness. Got home, and changed shoes then went out for a 4 mile walk (pub lunch half-way round - gotta have an incentive!). Limped the whole way. But... TBH, the walk did help. Today the soreness and tightness is much reduced. Walked 2 miles to work and the only discomfort only happened after I'd been sitting down.... which proves the theory - keep moving!
Unless anyone's got any other theories, in future, unless the pain is excrutiating, I shall keep moving with it.