Hello, I am in my 3rd week of a c25k program. This is the second time starting it after I had unbearable shin splints and knee pain and I found out it was from heel striking. I decided to start the program again with midfoot/forefoot strike. I was very happy to find how much easier and pain free it was. Until now... I just started getting ankle pain on the inside part of the ankle along with Achilles pain. It now hurts when going down stairs and walking. I was sedentary before this and I am 6'3 260 lbs. I am stretching and foam rolling and I was also fitted for proper footwear using a gate analysis to correct the over pronation. I am not pushing hard at all. Does anyone have an idea what this is and how to stop this from happening? I am actually starting to like jogging but it seems I keep getting injured even after taking all preventative measures. I have a picture of where the pain is outlined in ink. This is the inside of my right foot. The pain is where the ink lines are drawn and all in between the parallel lines.
Switching to midfoot from pronation is going to be a mixed bag of good and bad. At first you get relief from the wear and tear of excess movement, then you eventually feel the wear and tear of starting all over again. You need to allow time for your body to adapt to any new movement, even if it is more efficient than the old way. Think of how many years you spent working up to your old style, bad as it may have been.
At 260, any strategy is going to require strength of form. Did you do any exercises to prepare for midfoot, or just switch cold turkey? Some really light runners get away with a lot of faults in form, but for you, it's gonna hurt. My guess is your Tibialis Posterior is now working harder supporting the arch, since it is a supinator. The pain pattern is typical of one produced by this muscle, sub Achilles where its tendon slides. It will take a while for it to build up from the old pronation, where the muscle just lets the foot fall flat.
Tib P. is also a plantarflexor, so exercises involving plantarflexion, and supination can build it up. Right now, it is probably sore, so I'd back off a while, start back slow with exercise. and eventually get back on the road.
If you can get past the accent, this gentleman shows an exercise for strengthening the supination and plantarflexion simultaneously: