does cardio kill gains
Rajesh Panda

Rajesh Panda

Founder And Chief Editor, FitnessRhythm

Does cardio Kill Gains?

So I’ve gotten this question so many times, The question is does cardio kill gains? The Short answer is no, Cardio does not kill gains if done correctly along with maintaining a proper diet.

But before we can determine if cardio actually kills gain, we need to really understand what you actually need to build muscle. We can then determine whether or not cardio looks like it would be detrimental to muscle gains hypertrophy based on that criteria.


So what do you really need to build muscle? There are three main things. Firstly You need to be in a caloric surplus, secondly you need to be eating adequate protein. This is something most people do wrong. And lastly, you need to focus on progressive overload in your training. 


And progressive overload is just a fancy way of saying that you need to lift heavier and heavier weights over time. That means that you’re increasing your strength, which is a very good indicator for muscle gains.

So let’s break this down into more detail and analyze if cardio actually detrimentally affects any of these. So the first thing that we talked about is that for you to build muscle you need to be in a caloric surplus. So to build muscle, you need to be in a caloric surplus period.


 Unless you’re a complete beginner, a complete newbie to weight training. But even if you’re a complete beginner and can gain some muscle in a caloric deficit, a caloric deficit is still not optimal for muscle gains. So generally speaking, we’re going to say you need to maintain a caloric surplus to gain muscle at least for optimal muscle gains.

So cardio does burn calories. That’s pretty obvious. We all know that which in turn has led people to claim that cardio will stop you from building muscle and even that it might even burn muscle because it actually helps stop you from achieving a caloric surplus. 


So if you don’t eat the calories back that you actually burn from cardio, then you’re going to be ending up dipping into a caloric surplus. Most likely it depends on how many calories you eat in a day and how much other activity you have. What are your basal metabolic rates, what’s your metabolism actually is.

So there are lots of factors to consider. But cardio obviously burns calories and if you do too much cardio and you don’t eat back those calories, you’re going to dip into a caloric deficit. And if you’re in a caloric deficit that’s not optimal for gaining muscle, in fact, most people will not be able to gain muscle in a caloric deficit. 


So that is possible like that means that cardio could be detrimental to muscle gains, but only if you’re not doing your calorie intake, right? But even still, that doesn’t mean that your body is going to automatically start breaking down muscle for fuel if you dip into a caloric deficit.


You can actually use the caloric deficit intelligently for the purpose of shredding fat. The way you do that is by taking a high protein intake and maintaining a moderate calorie deficit while focusing on heavy compound weightlifting.


That way you can maximize fat shredding while at the same time maintaining muscle mass. So your body isn’t automatically gonna break down muscle for fuel. In fact, carbohydrates in your body are a preferred source of energy. 


And after your body has really consumed all the carbohydrates that you’ve recently consumed in meals or in snacks, then your body is going to tap your stored carbohydrates in your muscles and liver for fuel. And these carbohydrate stores are called glycogen. 


So you store glycogen in your muscles and liver and you can use those stores later for fuel. So glycogen stores vary in each person. It depends on a lot of factors, but muscle glycogen typically provides about 1400 to 2000 calories for about 350 to 500 g of glycogen, which is roughly enough for about 90 minutes of endurance exercise for the average adult. 


So when your glucose and your glycogen levels are depleted, they’re not available anymore. Then your body will preferentially break down fatty compounds known as triglycerides, which are present in fat tissue.


So fat, if you don’t know, has nine calories per gram and that’s more than double the four calories per gram in both carbs and protein. So fat actually provides a very efficient high energy fuel source. It’s not your body’s preferred source of energy carbohydrates are, but it is a very efficient high energy fuel source. So thankfully your body will metabolically prefer to preserve muscle. And when possible, it’s going to break down both carbohydrate and fat stores for fuel first. 


So you obviously need muscle tissue to survive, you need it to move. If you didn’t have muscle, you wouldn’t be living. So your body is going to do everything that it can to spare muscle tissue. So you’re going to work through your body’s carbohydrate stores and fat stores before your body starts tapping into your muscle tissue. 


So when your fat stores are extremely low or depleted, that’s when your body will then have to turn to protein. So after it goes through carbs, after it goes through your fat stores, it’s going to have to turn to protein. And when the glucose and fat stores are depleted, your body is going to have to turn to protein as I said, and it’s going to have to break down individual amino acids for energy.


So for carbohydrates and fat, your body can store those either as glycogen or as fat in the fat stores in your body, but your body does not store amino acids, that is why breaking down muscle is the only way to release amino acids for fuel. So, in typical conditions, when you’re eating on a regular basis and you’re not at a super low body fat percentage, your body will not use muscle for energy. And typically, protein is really only used for fuel in a starvation state. 


So it’s highly unlikely that you’re going to be tapping into your muscle and breaking that down.So no, you’re not automatically going to lose muscle, you’re not automatically going to lose your gains when you’re in a calorie deficit. 


So the answer to this first one is if you’re just kind of intelligent about it, like you don’t even need to put that much thought into it, But if you just eat the calories back and you’re not at a super low body fat percentage and just doing ridiculous amounts of cardio, then you don’t need to worry about cardio making you lose your gains. 

In terms of calories in versus calories out. So the second thing is that if you need to build muscle, you need to be eating enough protein. Now, cardio has absolutely no effect on this. You just have to be sure to hit your protein target, which really doesn’t change. If you decide to include some cardio in your training program. So cardio has no effect on the second thing that you need to build muscle. 


Now, the third thing that you need to build muscle as we talked about earlier is you need to focus on progressive overload in your training. Now, if you’re working for hypertrophy, which is just a fancy name for muscle growth, then you can still accomplish that with a mix of cardio and resistance training. 

The number one driver of natural muscle growth is progressive overload. Which as we talked about before, simply means that you’re lifting heavier and heavier weights over time. That’s a very good indicator that you’re building strength and muscle. But you can still create overload in a fatigued state. I wouldn’t necessarily recommend this.


 It’s not optimal for gains, But is a way to create overload. So you could do cardio even before or after resistance training workout. It’s actually a different stimulus to the body than a quote unquote fresh overload, which you would likely have during your first few sets of a normal resistance training workout. 


Now lifting heavier and heavier weights over time with proper form. As I said earlier, is a very good indication that you’re gaining strength and therefore muscle, but you don’t necessarily have to be completely fresh to achieve overload. You can actually be in this fatigued state. So no cardio doesn’t necessarily mean that you can’t be working on progressive overload in your training. 

So let’s recap what actually kills gains. There are three things,not eating enough calories, not eating enough protein and not applying the principle of a progressive overload, whether you’re in a fresh or fatigued state. 

So now that we’ve really looked at the three main things that you need to build muscle, and we’ve determined that cardio won’t, it doesn’t look like it will kill gains if you program it intelligently.


In reality, we’ve only really kind of scratched the surface of this question. There’s a lot more to cover. There are many other factors that we really have to consider, like training intensity, training frequency, training modality and training timing. So, to start diving into these other factors, let’s actually compare elite marathon runners to elite bodybuilders. 


So elite marathon runners obviously focus a ton on cardio and they complement all of their running with resistance training. But elite bodybuilders, on the other hand, obviously focus on resistance training and they complement their training with cardio. From these extreme examples, it’s really easy to see that muscle adaptations can differ greatly in response to aerobic training versus resistance exercise. 


You just have to look at the top marathon runners in the world and the top bodybuilders in the world. And you see there’s an obvious difference, even if you look at the top natural bodybuilders. So we’re not even talking about drugs and the effect that drugs should have on someone’s physique. 


You’re looking at elite marathon runners versus elite natural bodybuilders. You can see that depending on how you structure your training and how you structure your nutrition. You can have vastly different results, even if you’re doing the same, you’re doing cardio and resistance training, the way that you program it is really the difference in determining what your physique actually looks like. The more that you train for one of those, the harder it’s gonna be to really reach the same level in the other. 


So, an elite natural bodybuilder can’t go out and run a two hour and 10 minute marathon. That just doesn’t happen, and an elite marathoner probably isn’t going to go out in a bodybuilding show, so the point here is that you can’t really reach the same level in each of them, especially if you’re trying to get to the top of whatever thing you’re focusing on. But the point here is that aerobic and resistance training aren’t incompatible when we’re looking at real world studies. 


So now you might be thinking that all sounds really logical, but why do most people in the fitness community believe that cardio kills gains? Well, it actually started with a handful of studies that were published decades ago. And all of these studies were actually compiled and analyzed in a 1999 meta analysis conducted by researchers at the University of Queensland and also at the Australian Institute of Sport. So a total of 11 studies were included in this meta analysis. And they had all explored the interference of concurrent strength and endurance training. In other words, the interference of cardio and weight training.


So, five of these 11 studies in this meta analysis found interference in strength developments when you added cardio to a weight training program. One of the studies in this meta analysis found the interference in endurance development when both cardio when endurance training and weight training were combined. And the remaining five studies in this meta analysis found no interference effects income, current strength and endurance training. 


So it doesn’t seem like you can really draw any conclusive statements from this because five of the 11 studies found interference and five found no interference. Yet researchers began their published meta-analysis by stating that “concurrent strength and endurance training appears to inhibit strength developments when compared with strength training alone”. They went on to say that quote. 


Our understanding of the nature of this inhibition and the mechanisms responsible for it is limited at present. This is due to the difficulties associated with comparing results of studies, which differ markedly in a number of design factors, including mode frequency duration, and intensity of training, history of participants, scheduling of training sessions and dependent variable selection. 


And in an attempt to really explain the inhibition of concurrent strength and endurance training. The researchers hypothesized that qu “skeletal muscle is placed in a situation of conflict when concurrent training is performed, the muscle is attempting to adapt to both forms of training. However, this is not possible because adaptations to endurance training are often inconsistent with adaptations observed during strength training”. 

But there is a pretty huge missing piece to this puzzle that the researchers noted in their published findings, they said  “The effect of concurrent training on strength development in different muscle groups has not been systematically investigated”. In fact, one of the five studies that this meta analysis used to confirm their hypothesis that cardio interferes with strength development, even found that lower body strength but not upper body strength development was compromised when running was added on top of a strength training program. 


So they had a strength training program. There were 56 male rugby players that were used as subjects in this 1994 study that was published in the Journal of Strength and Conditioning Research and these 56 male rugby players, we’re focused on doing a strength training program and then the researchers added cardio in the form of running on top of that. And they found that lower body but not upper body strength development was compromised. So that’s a pretty kind of obvious finding that’s something that you might expect. 


But The whole point of this is that this 1999 meta analysis seems to really be less conclusive than its abstract seems to claim. But thankfully, we do have more current research to rely on. Only recently have human experiments offered support that this Interference effect could actually be due to incompatibility between cellular pathways controlling protein turnover, which is the continual process of protein synthesis and degradation. 


In the year 2012, study from the University of Sweden on 10 healthy, moderately trained men between the ages of 21 – 29 completed a five week program to test the changes in quadricep volume, cross sectional area and signal intensity between an aerobic exercise and resistance training program versus just a resistance exercise only program. So this is a small study size with only 10 people, but it was well designed. Each of these 10 subjects went through both training protocols and you might ask, well, how do they do that? 


Well, actually one leg of each subject was assigned to concurrent aerobic and resistance exercise, whereas the opposing limb was subjected to resistance exercise only. So again one leg of each participant of each subject was doing cardio plus weight training, and the other leg was doing weight training only. Now the aerobic exercise in this study was one legged stationary bike. I am not exactly sure how that works, but anyways that’s what they were doing for cardio. And the resistance exercise was unilateral leg extensions that were performed for four sets of seven reps with maximum resistance. 


It’s also important to note that the aerobic exercise was performed six hours before the resistance exercise for every single subject. Okay, so what were the results from the study? The researchers determined that increases in strength and peak power were comparable in the cardio plus resistance training group with a 9% increase in strength and 29% increase in peak power. And the resistance only training group with an 11% increase in strength and 24% increase in peak power. Okay, so the increases in strength and peak power were comparable in both the Cardio Plus Resistance Training Group and the Resistance Only Training group. However, the Cardio Plus Resistance Training group showed a greater increase in quadricep volume Than the resistance only training group with 14% vs 8%. 


The Resistance Training Plus cardio group also showed a greater increase in muscle fiber cross sectional area than the Resistance Only Training group 17% versus 9%. And quadriceps. Signal intensity increased 12% in the cardio Plus Resistance Training group, but not at all for the Resistance Only Training group.  So, the results really suggest that “the increased aerobic capacity seen in the Aerobic Plus Resistance Training Group is accompanied by a more robust increase in muscle size compared with Resistance only”. That’s very interesting. 

So if your main goal is to improve your explosive strength and power, then high frequency cardio probably won’t really help you. But we don’t just train for strength, at least not personally, we train to build muscle. We do want to get stronger but we really want to become more athletic, more functionally fit. 


So if that’s your goal then cardio can really help to complement your outcome. Okay, so what’s the main takeaway here? When programmed correctly cardio can help improve your results, your body composition and your overall health. Resistance training, coupled with 2 to 3 days of light to moderate intensity cardio can lead to greater gains in strength training alone. But there are two important considerations to keep in mind. For one. 


You want to add cardio but you don’t want to go crazy. So as I said, 2-3 days of light to moderate intensity cardio are probably optimal for muscle gains. For two, you should try to separate your cardio and resistance training sessions by at least six hours to minimize any chance of interference between the two. 


And don’t forget, cardio, which is again short for cardiovascular training is vital to optimal health and aerobic capacity.Our goal is to get into the best shape of our lives and that’s what we want to help you to achieve as well. We want to have incredible physiques, but we also want to be strong, athletic and super healthy. And I’m sure that’s your goal as well. So don’t skip cardio. That’s going to be a rap for this article.

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