First, a couple of things about the use of the word ďcardioĒ.
There really are only 2 types of exercise: aerobic and anaerobic.
When you do aerobic exercise, it means that youíre body has enough oxygen to keep you going at the intensity that you are currently at. When you do anaerobic exercise, your body does not have the necessary oxygen at that time to keep you going, so it has to use other energy systems to keep you going. And the two systems donít work separately, meaning, you tend to be doing aerobic with increments of anaerobic mixed in at times, and anaerobic with increments of aerobic mixed in.
For example, you start a walk outside and you are walking at a slow pace. Youíre not getting fatigued because your aerobic system has plenty of oxygen to keep at that intensity. But then you pick up the intensity and start walking faster, or maybe even into a run. Youíre anaerobic systems start to kick in since youíre aerobic system hasnít taken in the oxygen needed to support that new intensity. So you start breathing in more air, the heart starts pumping faster, and oxygen is being moved quicker to your muscles. After a little bit, youíre aerobic system has adapted to the new intensity and the anaerobic system decreases itís energy output, since the aerobic system is able to handle the new intensity.
You tend to use the anaerobic system more during high intensity, short duration activities that give you short burst of energy. Examples are when you are doing something like a 100-meter sprint, or lifting weights. Youíll use the anaerobic system to perform those activities, and then the aerobic system will kick in to help with the recovery.
Second, on to the issue of losing weight using aerobic or anaerobic, aka ďcardio vs lifting weights.Ē
Thereís a method after you workout for how your body recovers called Excess Post-Exercise Consumption (EPOC). Basically, after you are done working out, youíre body still needs an increased amount of oxygen than what you needed prior to working out in order to recover and repair the damage done to the muscle and nervous system. The longer this EPOC period lasts, the more calories you are going to burn in order to repair that damage.
So if you did something like a steady state run, after you are done, youíll have an EPOC period of probably a couple of hours which may involving burning letís say 100 more calories. But, after you get done strength training, your EPOC could last from anywhere between 12-48 hours, and could involve the burning a several hundred more calories because the repair that is needed for the muscles and nervous system are much more extensive than it was with a steady state run.
This is why more and more information is coming out and determining that the best fat loss methods involves some type of strength training along with interval training. In interval training you, are using short bouts of high intensity movements, with rest intervals to recover (like a full sprint for 30 seconds, with a recovery of a walk for 2 minutes, then repeat). Because you are using a high intensity movement for a short duration of time, itís causing more damage to the muscle and nervous system that requires a longer period of time for recovery than a long steady state exercise.
Another thing. Donít think that when you are doing strength training that you are not doing ďcardio.Ē If you are using a fairly moderate intensity, youíll find that youíre gasping for air in between sets.
Michael Navin, CSCS