I changed from heel strike to mid foot running 6 months back. Recently restarted my practice with relatively short 5KM runs @ 11-12kmph. After around 1-1.5Ks my calves started to tighten up and pain a lot. However, if I change to forefoot strike in the middle of the run, the calf pain goes away... returns if I resume midfoot.

Any ideas how I can manage this... fore/front foot strike is great but dont think I can do a lot of mileage on that as of now.