Jester is absolutely correct, however if you are having any joint issues, I would do the 15s anyway, then skip to the 5s right after the 15s. Due to your job, you need to go heavier during your cycle, but you don't want to mess up your joints. I would do 2 weeks of 15s, then 2-3 weeks of 5s, along with 3-4 weeks of post-5s. It may be hard to increment well, but you should be able to figure something out. Doing negatives during post-5s would be optimal, but if you can't do that, I would try clustering so you can go much heavier than your 5 RM.