This will vary, but the requirements should be provided to anyone who inquires. Very, very early in my time on Yahoo Answers, I was able to find the requirements for one city on their website to answer a similar question -- so if you tell me which force you are attempting to learn about, I might be able to find it.
I also had a patient who was moving across the country to join he force in a major city on the West coast, and he had hearing loss from military service. Fortunately, their guidelines were very specific, and he was actually able to meet there criteria. Of course these requirements are to for ENTRY to the academy or force -- they don't seem to perform routine fitness evaluations! LOL!