I get the same thing. With me, it's actually the way I run - I have high insteps and overpronate. I've managed to get through a half marathon and 10K with massages and lots of stretching in the weeks running up to the races, but in general it's not good!
I know I need orthotics, and have finally given in and am going to get some. Maybe you're the same - I'd recommend getting someone (e.g. sports phsyio) to have a look at it.
However in the short term for the GNR, I'd get some massages done, (you can also do them yourself), and stretch out your calf regularly on a daily basis. If they tighten up during the race stop and stretch out.
I'm doing the Nike 10k on Sunday and have developed a slight pain in my left calf. I know it's because I over pronate and should have orthotics, but in the short term I need a physio! Can anyone recommend one in the central London area? I've tried all the BUPA wellness clinics but they don't have any availability.
I have extremely high arches and have been told to get orthotics as it is affecting the way I run and I end up hurting my calf muscle in one of my legs when I train too hard (as I am at the moment!). However, I was recommended a podiatrist and when I phoned he quoted £400 !!! Can anyone provide advice/help on this matter (I live in London if anyone knows of someone else I can try).
Have had my application for the Marathon sat on the table at home for the last month, debating whether to post it. Probably will!
What I think may work is if I cycle/cross train during the week and then maybe do a short and long (1hr) run at the weekend.
Problem also is due to bad posture etc., I strained my soleus a week before Windsor. Although it was all right for the race, (due to lots of rest and physio), it still isn't quite right. Guess I just need to get my act together and sort out orthotics and improve my posture....