Shoes and flat

Just ran 45' with shoes on flat, very easy pace. No sensations at the Achilles tendon during the run. Now that it is cooling down, I begin to feel a very light sensation, nothing worth worrying. But still something. However, as expected, much better on flat. Will keep running with shoes on flat for a while. Then introduce some 5Fs, slowly, easy. Indeed, confirmed, went again 4 days later, 60' with shoes on totally flat track. No problem at all, absolutely no feelings in the Achilles tendon. Thus it was clearly due to the combination of barefoot and hills. I was extremely tired while running, went slow, but the important bit is that I had no feelings at all in the tendon. Next, I will slowly go back to 5Fs, first on flat and introduce hills very very slowly. Important lesson here, barefoot + hills is not good, you have to take it easy on this too. Went again 3 days later, slowly increasing the pace and the length, introducing some hills. 66', first half with my daughter following on bike, easy pace with some sprint between us. Second half alone and faster pace. No problem on the Achilles tendon. It was thus indeed the hills the problem. Next time, will go barefoot, easy and flat. Keep on running.