In reply to the original post, I had exactly the same problem, especially as this release had a lot of lunges, with changes in direction, etc. Our instructor has since mixed it up a bit, but she recommended I get inserts to support the arch. I went to a shoe store (best if it specialises in sport shoes, etc.) and got them fitted to my runners. Essentially, they're shock and arch support. Now, there is a lot less pain. A little discomfort, but I think that's pretty normal considering I do Combat, then Attack right after.
Good luck!
Combat: Attack: Pump