Physical stuff to get hired, certainly. Not sure about within the Academy, but they'll certainly encourage you to get fit. No sense graduating too fat/slow to pass the physical agility test of a department.
Whatever else you do, work on your basic math skills, and work hard on your writing ability. Learn to write complete sentences, recognize bad spelling, and know the difference between their, they're, and there. It'll make your work experience much easier (and long-lasting)
. It doesn't matter how good of a cop you are if you can't write a decent report about what you did, or saw.
Oh, and have a back-up plan. The average person changes careers something like 3-5 times (?) in their life these days. I'm on my third.
Although it might seem to be your one true dream, be ready and able to do something else. If nothing else, until you land your dream LE job. Security enforcement at $7/hour might be great for LE-related work while you're going through school, but as a long-term career,