Cardio exercise equals muscle loss?

people say cardio killz gainz because it eats up calories that could otherwise be used to repair muscles. thats about it really, so if you eat enough then there is no reason not to do some cardio

Got to be a troll as there are so many reputable sites including several university studies that address this.

Not if adequate calories are supplied.

Muscle loss happens when it's not used (atrophy) and extreme calorie deficit is present.

A.C.E. Certified Personal and Group Fitness Trainer
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Kickboxing Certified Instructor
Been in fitness for 30 years and have studied kinesiology and nutrition

Short answer: Cardio does not automatically burn muscle -- this is a myth. Muscle tissue is not your body's preferred source of fuel.

Longer answer without being too technical: Exercise will burn the easiest energy source available. If you are eating, this is probably from the food you eat -- carbohydrates, fats and proteins. There are some circumstances where your body will burn muscle, but this should not be the case if you are eating properly.

Muscle tissue is made up mostly of protein, which, in turn, is made up of amino acids. Normally, your body does not use protein to produce energy. If you run out of glycogen stores, however, and no glucose is available, your body will then break down its own muscle tissue to release amino acids. These amino acids are sent to your liver, where they are converted to glucose in a process called gluconeogenesis. When your body starts to use muscle tissue for energy, you lose muscle mass.

But unless you're starving yourself to begin with, and if you are I doubt muscle retention is your concern; you would have be to doing some extreme level endurance events to get to this point. Like 3+ Hours.

If your cardio is less than an hour, I doubt losing muscle mass is anything you need to be concerned about.

I would add to this great post that if you are participating in endurance events, the risk of muscle loss can be mitigated and managed through proper nutrition while you are riding or running or whatever it is you are doing as well as proper pre and post nutrition.

On my recent 1/2 Century, I knocked back a Cliff Bar along the way...additionally I consumed a small bag of dried fruit, half an orange, a pickle, some chocolate milk, sucked on a jolly rancher every 30 minutes or so, and drank plenty of coconut water. I also properly fueled myself the days leading up to the event as well as a nice bagel in the AM and followed up with a recovery smoothie that was high in protein as well as carbohydrates...which I consumed while eating a cheeseburger and potato salad.

I was OK...

ETA: the greatest risk of muscle loss comes with excessive exercise without any understanding of what is required to properly fuel one's body. Your greatest risk of muscle loss is eating at a huge calorie deficit and then making that deficit even bigger with excessive exercise that isn't fueled. A modest calorie deficit for weight loss combined with a good, progressive lifting routine and adequate protein intake is going to mitigate muscle loss.

If you understand that doing **** tons of exercise also requires **** tons of food (even when you're trying to lose weight) then you'll be ok...if you have no idea how to properly fuel your body then you might run into issues here if you're doing tons and tons of cardio and endurance work and eating like 1200 calories per day or something...