Upgrade Your Workout: The Best Extreme Sports to Try

Thinking about taking your fitness routine to the next level? Smart idea, as research shows the secret to staying in shape is learning how to keep your body on its toes. "Fitness goers want to be challenged, and sometimes going to the gym isn't enough," says Pete McCall, exercise physiologist with the American Council on Exercise. Here, McCall offers smart and exciting ways to upgrade your workout, whatever your sport.

Sick of Running Around in Circle?

If you're the queen of 5Ks, it may be time to expand your kingdom to include some obstacle courses, like the Warrior Dash or Spartan Race. With both race series scattered across the country and happening all year round, you can sign up anytime for the hard-as-hell three-milers that guarantee to engage more than your legs. "A lot of the obstacles -- mud pits, tunnels, and wall climbing -- require upper-body strength, coordination, agility, and flexibility, so they really challenge you to move completely different than you're used to," says McCall. "Interval training is key for this, so instead of just running in the park, you'll need to do sprints and pull-ups."

A longer option for half- and full-marathoners is the Tough Mudder, a 10- to 12-mile obstacle course created by British Special Forces. The series, which currently features 22 events around the globe, just teamed up with 24 Hour Fitness to offer 60-minute boot camp classes to members ($15 for non-members), complete with belly-crawling, wall-climbing, and mud-slogging moves, to help you get race-ready.