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Can Cardio Kill Muscle?

By Joe Talarico on Sep 23, 2020 10:00:00 AM
5 Minutes Reading Time

The short answer is yes. The answer to this question is probably the most faced issue I have with the majority of my clients. The reality is, losing weight isn’t hard. Losing weight while maintaining muscle on the other hand, is more difficult.

Most clients I get whose goal is fat loss usually don’t come to me fresh. I get individuals who are most likely already doing 4-5 days of spin, Orange Theory, bootcamp, or running on the treadmill like a mad man. They choose all the highest intensity versions of cardio because they think “the harder I go, the more calories I burn!”, while also eating as little as possible to further maximize the deficit. While sure, they aren’t wrong, you still have to factor in muscle.

What People Don’t Realize About Overdoing Cardio

Your body is built for survival. When you do what was mentioned above, for the first couple weeks, absolutely, your body is a calorie burning machine. As the calories get lower, and the energy expenditure gets higher (because you keep wanting more), your body has a decision to make. It doesn’t realize you WANT to lose weight. In fact, it thinks all this extra stress has been put on your body without the proper intake of food to match so it halts fat loss. That’s right. In order to “save your life”, it starts prioritizing what’s important and what’s not. Fat is a very good energy source. The whole reason we have fat stores was because back in the day, we might have gone days without food. When you’re eating too little calories and doing 5+ days of cardio your body is thinking the same thing.

Muscle costs a lot of calories to have, and cardio doesn’t require large amounts (like resistance training does), so after a couple months it’ll start burning through your muscle and holding onto fat, in order to provide you with energy. If you ever hit a point in your diet where you plateaued even though you’re starving, and doing all this cardio, you’ve hit that point. Technically, if you didn’t care about muscle, you could get rid of the plateau, and keep lowering calories and losing weight. There really isn’t such a thing as stalling fat loss forever. Just look at the prisoners in concentration camps. Do you think they ever hit a point where they “just couldn’t lose fat?” I don’t think so.

The Solution

Okay, so we know eating too little, and doing too much cardio can in fact burn up your hard earned muscle. So what do we do then? Lift heavy weights.

Remember, muscle is calorically expensive to have. BUT, your body is also built for survival. It only burns up the muscle if it doesn’t feel there’s a need for excess amounts of it (AKA when all you do is run). However, if you give it a proper stimulus, such as a workout session where you hit your full body, with different exercises, staying 1-2 reps shy of failure, it’ll hold onto it. Proper resistance training sends a signal to a calorically starved body “Hey, there’s this excess stress being placed on our muscles a couple times a week! We better keep this muscle so we can withstand this stress!”

Even if muscle gain isn’t your goal, there is no sense in losing whatever muscle you currently have. Even for the ladies who say they don’t want to look “bulky”. Do you want to look “tone?” Guess what that “tone” is? It’s muscle. Do full body workouts 2-3 times a week at 2 reps shy of failure. Stick to compound lifts mostly.

As for cardio, the worst thing you can do is unfortunately what I see the most. Either HIIT training multiple times a week, with no resistance training and low calories, or running at a moderate to hard pace on the treadmill for 30-50 minutes everyday with no resistance training. Both are recipes for killing muscle and keeping fat long term.

In addition to your 2-3 full body workouts, start with 2-3 days of cardio. Two of them should be low intensity, steady state cardio (heart rate is usually around 130-140bpm). This ensures the intensity is high enough to prioritize fat burn, but not tap into the muscles. Use the other day to do HIIT cardio at 15-20 minutes with 5-6, 30 second sprints in between. If you aren’t a fan of slogging away on a treadmill or at the gym in general for cardio, considering increasing your NEAT activity. Focus instead, on hitting 10,000 steps throughout your day. Every week add 1,000 steps for the duration of your fat loss phase. Again, the intensity is very very low so the most muscle will be preserved. For most people, it’ll be easier to incorporate into their lives and hold onto, versus trying to find time for cardio at the gym.

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Joe Talarico

Joe is a certified Precision Nutrition and strength & conditioning coach. He assisted the UCLA Women’s Tennis team in winning their 2014 NCAA Championship Title, as well as study under the great strength coaches at Pepperdine University. He was a collegiate rower at the University of Rhode Island (where he got his Kinesiology degree) as well as an amateur physique competitor. He is currently the master trainer at Upgrade Labs in Santa Monica where he is combining his years of training clients in the gym with newer technology to optimize their performance and recovery. He also cohosts The RelationSH*T Show Podcast with his fiancée where they discuss all relationship topics unfiltered from who pays on dates, to open relationships.

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