Most people use fitness solely to help them lose weight or get in better shape. However, others have found that working out and building a better physique can also be a great way to earn some extra cash—sometimes into six figures (or higher). How do they do this?Pro Bodybuilding. One way to earn a lot of money using fitness is to become a professional bodybuilder. A lot of top competitions pay at least this amount, so you can easily earn $100,000 or more annually by winning just one event, that is, as long as you place in one of the top slots.Should this be the route you want to take, your first step is to start entering fitness competitions. Once you start catching people’s eyes with your medal-earning physique, companies will want you promoting their goods, which will raise your wages even more.Fitness Modelling. Another option is to become a model for fitness magazines or related publications. The going rate is somewhere around £3,500 ($5,000) per day for men and £8,000 ($11,500) for women, which means that you can make a six-figure income by working fewer than 30 days per year. If this interests you, make sure you have some good photos to send out. This means paying a professional to take them as he or she will know how to highlight your physique in a way that gets the talent scouts’ attention.Personal Training. Granted, most personal trainers don’t make $100,000 per year setting up personalized exercise plans or teaching group fitness courses, but the really good ones make much more than this…especially if they land a client who is a celebrity or otherwise well-known and in great shape (thanks to you).You can also use your experience as a personal trainer to develop a new exercise program or shoot workout videos. This raises your income even more and, once they’re done, you get to just sit back and cash your checks.