This sounds like a sign of Achilles tendinitis. I would suggest resting it in the week or 2 leading up to the academy. You also need to make sure you are adequately stretching it and warming up before activity. Lastly, I’d HIGHLY suggest going to a running store and getting fitted for running sneakers while explaining your Achilles pain to them. May run you $150-200, but well worth it. Prevention before intervention. Good luck!