Tightness in calf

Can anyone give me any advice on this one. I have been feeling some discomfort in the back of my right calf muscle. I can only really describe it as a knot like feeling in it. I only seem to feel it during climbs and it gets no worse during the ride. What advice can people give me as to try and stop it, maybe try changes to seating position or what else can i try?
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http://www.cyclefitcentre.com/pdf%20fin ... _final.pdf
Specialized Roubaix SL3 Expert 2012, Cannondale CAAD5,
Marin Mount Vision (1997), Edinburgh Country tourer, 3 cats!
After a bit of faffing about I tried some different shoes (MP66s) and the problem went away. I think my old three-strap shoes were too stiff and of course the temptation is there to ratchet them up tight. Clipped-in rigid shoes, legs going round and upper body moving about think about it something has to give. The MP66s are stiff enough for trail riding but the uppers are more flexible and easier on the legs.
Thanks guys.