You’ve seen exercise balls lying around the gym, sporting goods store and even the office. You might think it looks silly, but the exercise ball can give you some serious results. Here’s what you need to know about finding and using an exercise ball. Incorporating this fitness tool into your training routine will have you rolling towards faster PRs in no time.

First and foremost, you need to buy an exercise ball that’s right for you. Shorter people will want one in the 55 centimeter range. A tall person will find a lager exercise ball (65 to 75 centimeters) much more comfortable. You want to find a fit that allows your hips to rest even or just a little higher than your knees when you are sitting on the ball.

Once you have your ball, you can get a workout just by sitting on it, Your leg and core muscles will be engaged as you balance on your exercise ball at your desk, when you watch your favorite show, and of course when you exercise on it. Crunches, stretching and weight training can all be amplified by being done on an exercise ball. Google for specific workouts for your needs, be they core strength, flexibility or isolated strength training. (Or all three!) If you want more direction, look for training DVDs for exercise balls. They are very effective and lots of fun. Your kids might think it’s a toy, and that’s okay. You can always get a good workout goofing off with your biggest fans.