First, it is helpful to understand your objectives. If you are training to add and preserve muscle, OR to burn fat, it is instructive to note that if you consistently perform your cardio at a high intensity level, you may be burning muscle! This is a little understood element of cardio training, weight loss and muscle gain. You don’t want to cannibalize your muscle, because 1 lb.. of muscle  will burn 50 calories at rest. Further, if a woman, you don’t need to worry about getting “big and gross” unless you’re taking testosterone supplements! Muscle is good, so don’t burn it off.

There, that said, there are three cardio zones, from Zone 1, low intensity, to Zone 3 high intensity. Each zone is a percentage of your maximum heart rate. Zone 1 is in the 65% to 75% of your maximum heart rate. Zone 2 is 76% - 85%, and Zone three is 86% to 90% of your maximum heart rate. Your maximum heart rate is calculated by 220 minus your age.

If you’re an intense bodybuilder or powerlifter, a 20 minute walk in Zone 1 will burn fat and not muscle. For me, that’s 113 - 120 beats per minute, although as I get fitter the zones tend to slide up. Currently as of this writing, I’m really not breaking much of a sweat until I’m closer to 120 bpm but that isn’t a taxing zone. Every body, age, and capacity is different, so your Zones 1 - 3 will be different. However, using the Max heart Rate X % will give you the right zone.

Now a word on interval training. After lifting, you’ll burn maximum calories (and less muscle) if you never exceed one minute in your Zone 3, followed by a minute in your medium intensity zone or Zone 2. This is a good way to train and will be dealt with later.

In summary, if you’re trying to lose weight or add muscle, both of which are almost synonymous, you may be doing your cardio at a too high or too low rate. Many cardio machines now include electrode plates, so checking your pulse is easier than the finger on radial side of arm method. Check your heart rate frequently and determine if you are in the right zone!