Craving a new challenge? Try a triathlon, which incorporates swimming, biking and running all in one race. With more than 3.5 million participants worldwide, triathlons are more about personal goals than competition. A triathlon may seem intimidating, but the event has a reputation for being unusually welcoming and supportive to beginners. You’ll find everyone from the fastest finisher to the aging plodder cheering you to the finish line. The best part? If you’re already exercising regularly, it only takes six dedicated weeks of training to get you to race day.