Question: Is it true that doing cardio can make you lose muscle mass?

Hey chris, how often you do cardio??

And is it true that doing cardio make you lose muscle mass??
I am skinny guy trying to put muscle mass and love to swim a lot…
Don’t wanna leave swimming..

So here’s the deal: that viewpoint goes back to a misguided view of building muscle where the more calories you consume, the more muscle you will make.  While this is true in a vacuum, there are several other factors we must consider:
1. muscle mass is positively correlated with blood flow

2. hormones play an intervening role in building muscle

3. Cardio will help you stay healthy
4. You love swimming Not doing cardio at all could definitely lead to less blood flow to the muscle cells, which means less nutrients actually get to the muscle cells. This would obviously put a limitation on gains, and would probably give you some significant health problems. So cardio could definitely help with gaining muscle if not overdone.Second, we also have to consider hormones. An increase in fat mass could lead to less sensitivity to the hormone insulin. This means that your muscle cells stop responding to insulin, which is responsible for shuttling nutrients to their destinations in your body. If the muscle cells become insulin resistant, then the body has no where to store glycogen except for your fat cells. Again, this is not good for muscle growth.  Now, lets look at a situation where cardio could be negative for muscle growth. Take someone who is overtraining for a marathon and doing death marches every day (I’m talking 6 miles plus a day). In this case, the hormone cortisol could be turned on – which directs the body to burn muscle and store fat. This happens because your systems think you are in danger of dying from starvation and are looking for food. So they freak out and turn on this survival mechanism. In this case, where you are doing too much cardio, you could hurt yourself as far as muscle mass goes. On the other hand, most fitness professionals overstate this possibility and doing sane amounts of cardio would probably help you more than they hurt you. I personally do cardio everyday because I want to be healthy and because I enjoy it and it makes me feel good. I’m no Mr. Olympia, but I’m happy with the muscle mass I have and the strength I have.         Here’s the take home: if you love swimming, do it. You can still develop a great body without limiting your activity and becoming less capable of doing physical things. Chances are you’re more likely to get more out of doing a healthy activity that you love rather than conforming to someone else’s ideal of what you should look like. It will also make you healthier and more useful if your cardiovascular health is good. Continue to lift weights, eat well and follow good programming, and you will be on your way. Just don’t be in a rush. This stuff takes a lot of time.     Thank you for subscribing to my channel and for your kind words.