The goal of this article is to clarify how cardio and whether or not cardio goes hand in hand with bodybuilding as in gaining muscle mass. The general answer is this depends on the intensity of your cardio exercise.

High intensity cardio which resembles high levels of stress producing cortizol is detremental to building muscle mass. Yes, it helps you lose fat but it also stops you from building muscle. To better understand this effect, let’s take a closer look at the following terms:

mTOR: is a protein that is encoded by the mTOR gene. Some of the main activities of this protein is cell growth and protein synthesis. It integrates substances coming upstream into the process such as insulin, IGF-1 and -2 (growth factors with anabolic effects in adults) as well as some amino acids resulting in growing muscle tissue.

AMPK: is an enzyme made out of 3 proteins that is produced in larger amounts when glucose/energy goes down in your body and is produced mainly in muscle tissue, in the heart and the brain. AMPK has several roles one of them being fat burn and loss of appetite.

While these two sound like they are just great for the body and they are, the problem is they do not work together. When AMPK is produced is attaches to mTOR stopping it from integrating upstream substances resulting in inhibiting the protein synthesis process which is mainly responsible for muscle growth though it does help in fat loss.

Now when is AMPK produced that highly stopping mTOR from performing protein synthesis? High intensity cardio has a high load on the heart rather than individual muscles. This leads to the excessive production of AMPK in the heart that is carried through blood circulation to all the body and its muscles where it attaches to mTOR. The recommendation would be to perform low intensity cardio for longer intervals at a pace of around 2 to 3 mph or (moderately fast) walking that would not lower glucose levels triggering high production of AMPK.