Hopping on the treadmill or running the same path every day can get boring, and the repetitive motion can wear on your muscles. FitSugar says we should break out of the rut and include at least three types of cardio in our weekly routines. Make your three sports swimming, biking and running and you might just get yourself in shape for a triathlon. Hey, Kristen will convince you that the sprint tri is definitely doable for the average gal or guy.