Tennis is a very strenuous sport concerning your skeletal system – your muscles, tendons and joints are taxed tremendously with all the quick changes of direction and bursts of sprints and stops. And tennis being “one-sided” sport doesn’t help much either. Even if you play two-handed backhand, the dominant side of your body gets much more work – your serve, volley and forehands are hit with your dominant arm. Often, most players prefer to hit their forehands so they run around some backhands to hit the forehand, and with that your dominant side gets even more work. Over time, one side of your body gets little stronger, bigger and tighter. You have maybe already noticed that. No amount of work in the gym will make it even, but it’s a good idea to do it, so you would make the difference as little as possible.