I agree with USAF. This question comes up every yr and the answer is always the same; DO NOT WORK OUT THE DAY OR 2 BEFORE.
Plus, drink lots of water and NOT sports drinks for those 2 days. DS is going to get his final DODMERB (you get another one prior to commissioning) and he already knows:
1. No workout for 2-3 days prior
2. No sports drink, soda or caffeine (luckily he doesn't drink caffeine)
3. WATER, WATER, WATER
As others stated this is a DodMERB issue, I just wanted to give a cranium up for new posters so they won't make the same common mistake.