Is this a personal workspace or a public place? And what kind of lighting is in this room? Sunlight/incandescent/fluorescent lighting will affect your colors......
That having been said:
Warm colors like yellows, oranges and reds promote excitement because they are generally associated with warm things like sunshine, fire, heat. If you are using this room for stepping or boxing, a warm color might be a good choice, as it would pump you up subconsciously while you're in there. One of these colors might also work nicely if this room is on an Eastern or Northern exposure where you wouldn't otherwise get much warm lighting from the sun.
Cool colors like greens, blues and purples are calming and tend to be associated with things like water, trees and the sky. That would probably be a better direction to move in if the room is going to be used for something like yoga or pilates. Cooler colors also tend to open up a space and would help tone down the warm lighting you would receive in a Western or Southern exposure area.
Neutral colors like black, white, beige (or greige) might be a good option if your workout equipment is already loaded with color.
All this info is intended for you to assess your needs and help you make a decision based on the knowledge of your particular situation (and likes and dislikes!).
I really hope this helps. Good luck!