One way is to simply track your own workouts. Interval training can help you build endurance more quickly than steady state training, especially if you exert yourself far above your comfort zone, at about a level 9 on the perceived exertion scale. Doing an interval workout one or two times a week can boost your endurance and your calorie burn. These are usually administered by a professional at a gym or a lab and may involve working up to a very high intensity. The graded exercise test involves a long series of intervals on the treadmill while monitoring blood pressure and heart rhythms. The Bruce protocol test also involves working on a treadmill while your heart rate, blood pressure, and perceived exertion are monitored. Both of these are tests are accurate but may be costly. For this, you warm up and then walk a mile as fast as you can, either on the treadmill or outside. You record your heart rate and workout time and enter your results into a Rockport 1-mile walk calculator ...