There are several activities you can chose to build your cardiovascular system (walking, hiking, cycling, swimming, etc). You want to be able to sustain an elevated heart rate for at least twenty minutes.
In order to burn fat and build muscle you need to know your MAHR (Maximum Aerobic Heart Rate) and monitor it throughout your workout routine. If you increase the intensity of your workout routine, your muscles demand for energy will exceed the level of burning fat and switch to using carbohydrates. At this point you have exceeded your MAHR. Staying at a level at or about twenty beats below that number will help ensure you are not overtaxing your system. Becoming fit is not suppose to be painful or exhausting because this is one of the main reasons people quit.
Workouts done at the proper pace will burn fat and over time build your endurance level. This is best done at a methodical pace where you build up to and not push beyond the limits . In time not only will the fat burning efficiency improve but your body composition will change becoming leaner.
Remember...you are not in a race with your body as you work to become fit...the object is to find an activity you enjoy so your fitness program can last for your lifetime.
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