Running is fantastic exercise: Gets your heart rate up, burns calories, and it can even elevate your mood. However, if you just go for a 30-minute jog every day, you may grow bored and even unenthusiastic, leading to excuses not to train. Worse, you may eventually stop advancing your fitness.Like New York City bike messengers who work all day, you may become capable of incredible fitness feats, but your body begins to stagnate as it merely adapts to what you’re doing instead of being forced to make improvements. » Read more about: 4 Treadmill Speed Training Workouts to Get Faster and Improve Fitness »