In order to maximize the fat burning process during cardio while sparing muscle, the goal is to keep your heart rate at 65-75% of your maximum heart rate (MHR). Heart Rate can be monitored by pressing gently on one side of the neck with your index and middle finger until the pulse is felt at the carotid artery. Count each beat you feel to determine your heart rate. You can count for 60 seconds, or choose a smaller interval and multiply the value to determine a per minute count. Your maximum heart rate is calculated as 220-Age(years). So if you are 20, your max heart rate is 200. So 65% of your MHR would be 130, and your optimal fat burning range would be 130-150 (65-75%). Any higher than the max of this range will contirbute more to cardio endurance and increases in your VO2Max which is your maximum oxygen intake during physical activity. Although this is an important attribute to improve, it does not affect your fat stores as efficiently and can even lead to muscle atrophy if proper energy stores are not available.
In the gym, you can keep your heart rate in the optimal fat burning range simply by walking on a treadmill at a low incline or performing low impact elliptical, stepping or cycling machines. Any low exertion activities outside of the gym will also get you in this range. To get the most out of your workout, exercises should be performed, starting off, for 30 minutes. Later on, you can up your exercise duration to an hour to burn maximum calories.
We’re back from a week of travel, rest and holiday celebration. Needless to say, a week spent on a plane, in an airport, in a family’s house and out with friends does not bode well for eating healthy and sticking to your plans. Throw in the “mandatory” holiday meal(s), and the foods included, and anyone is bound to see their progress towards their goals falter a bit. 
