A friend from work asked me if I would be interested in trying Brazilian Jiu Jitsu. I had no clue what it was, so at first I was a little hesitant.
He said just show up and watch, and if you like it, you can jump in and try it out. It looked fun, so I asked if I could join.
My first full day of training, I vomited.
45 minutes of warm up and practicing a submission hold wore me out.
45 more minutes of grappling just about made me pass out from exhaustion.
Jiu Jitsu will workout your grip, forearms, biceps, triceps, back, chest, shoulders, legs, and core.
The core workout alone will destroy you that first time!
After a month of training, I had lost twenty pounds and improved my overall strength. I was able to shave  two minutes from my PT run time, and I could max the number of pushups and sit-ups.
The first PT test I took after starting Jiu Jitsu was almost like someone else took the test for me.

I’m not familiar with any other form of martial art, as Jiu Jitsu is the only form I’ve trained in.
Taekwondo, Karate, Thai kickboxing, Systema, Kung Fu, or any other I have forgotten are all good disciplines, and Jiu Jitsu might not be for you. But you might consider giving one of them a shot.

If you don’t like the gym, try the dojo.