How Cardio Impacts Your Gains

European handsome tattooed strong muscle bearded man in gym doing cardio ride bike

How Cardio Impacts Your Gains

Cardio, the thing that gym heads love to avoid. It’s become some badge of honor to avoid it. We joke about cardio robbing you of your gains, but I think many lifters take that to heart too closely.

So as the years progress, cardio has gathered quite the bad reputation in some circles. I partially get it because nobody wants the physique of a marathon runner. Those guys can’t get a date if their life depended on it. All jokes aside though, I think cardio is misunderstood.

Let’s explore how cardio impacts your precious gains, so bro-science stops spreading like wildfire.

Understanding Cardio and Muscle Loss

Bodybuilding circles often teach us that cardio causes muscle loss. Touching a treadmill will make you look weak and strip of your juicy biceps. On a purely physiological level, this is somewhat true. In trained lifters, cardio has no anabolic effects meaning it doesn’t grow muscle tissue despite the potential for muscle damage and muscle stress.

The mechanical tension is not specific enough for muscle tissues to produce hypertrophy triggering force.

So by nature, cardio is catabolic, not anabolic. This means cardio inherently breaks down instead of builds up. Fortunately, in most cases, cardio doesn’t breakdown muscle tissue, but rather stored and circulating sugar/lipid. It essentially metabolizes carbs/fat to fuel the act of cardio.

In fact, most studies where people consume sufficient calories/protein, cardio doesn’t cause any muscle loss. So while cardio is catabolic in nature, it’s not sufficient alone to strip you of muscle tissue.

Now if your lifestyle is extremely catabolic, then that’s a different story. If you get no sleep, have astronomical stress, don’t lift weights, poorly nourish yourself, and avoid protein like the plague, sure adding cardio will only make muscle loss worse. But for most lifters with a decent lifestyle, this isn’t the case.

The Interference Effect

However, cardio isn’t all innocent either. It doesn’t cause muscle loss, but it possesses what researchers call the interference effect.

To explain the interference effect, let me take you back to freshman Kinesiology class. Here’s the basic of how exercise changes you. What you impose on the body is a stimulus which is essentially a signal. This signal tells your body to adapt to the stimulus.

The signal that cardio sends is in slight opposition of the muscle building signal of strength training. This means that the adaptations or benefits of strength training like strength, hypertrophy, and power all get compromised when done within a lifestyle that also contains cardio.

It’s like spending time with your bros vs spending time with your wife. Sure, both relationships can coexist, but spending too much time with one relationship will impact the growth of the other.

So picture somebody doing a bunch of strength training throughout the week while also doing many sessions of cardio during the same week. The body is constantly getting opposing signals to adapt.

It will still adapt because the human body is amazing, but making some gains is different than maximizing your gains. Soit’s important to understand that cardio can limit the rate you build muscle.

Fortunately, we live in 21st century where we have smartphones, movie memes, and apps that let strangers pick you up. With our modern world also comes ample research on how to mitigate the interference effect.

How to Minimize the Interference Effect

So the most powerful way to minimize the interference effect is to simply reduce cardio volume. If you can reduce the volume, you’ve grabbed the low hanging fruit to make more gains from strength training.

You’ve also added more time and recovery capacity that can be devoted to lifting.

The modality and timing of cardio matters too. Extremely light and low intensity work like walking can be done at any time and in any amount as it shouldn’t have any interference.

But as you raise the intensity of cardio, the interference signal is stronger. In other words, if you can’t breathe through your nose or keep a conversation going, interference is present.

But interestingly, extremely high intensities beyond this point may be better. High intensity interval training may have less interference because it resembles strength training more from a molecular level. However, HIIT is more fatiguing than most training modalities which isn’t great for gains either. This will dip into recovery resources and lower strength training volume.

It’s no surprise many bodybuilders opt for low intensity steady state cardio. Their recovery capacity is maxed out from their high volume strength training.

In addition, lower impact cardio tends to have less interference as well. For example, cycling beats sprinting in this regards.

Timing wise, doing cardio and strength training in separate sessions is best. If you can’t do that, it’s best to do cardio after your lifting. This allows strength training to be at it’s highest.

If you’re doing lower intensity cardio like steady state cycling or rowing, you can also sandwich your strength training. So instead of doing an hour of lifting followed by 20 minutes of cardio, you do 10 minutes of cardio, then an hour of lifting followed by another 10 minutes of cardio.

The theory behind this is that by splitting your cardio up, you’re not doing any one bout that’s too significant in volume thus reducing the chance of interference.

Lastly, interference seems to impact trained lifters more than beginners. Trained lifters are closer to their genetic ceiling and need ridiculous levels of mechanical tension for further hypertrophy only achieved by strength training. On the other hand, a complete newbie who came off the couch can do as much cardio as they want. They’re so out of shape, even cardio can build them muscle thus contributing to hypertrophy instead of interfering with it.

But anyways, below are some cardio modalities that are low impact in which a hardcore lifter can choose from to minimize the interference effect.

Incline treadmill walk
Erg rower

Most the options above can be done for lower intensities for longer durations or for short bursts of higher intensities.

Should You Skip Cardio?

Then comes the obvious question. Why waste all this thought on how to mitigate the interference effect when you can simply skip cardio?

It’s a valid question and the answers for heart health is overrated. Lifting weights is also excellent for heart health in every study metric, although the impact is arguably smaller. Most lifters lift quite a bit though and their heart is working deeply hard to do so.

However, cardio still has it’s merits. Aerobic is not a bad word my friend.

You need a certain level of fitness to support strength training. This doesn’t mean you need to be in shape to complete a triathlon, but your VO2 max shouldn’t be limiting you and muscle capillarization is needed to maximize blood flow and nutrient delivery.

Your blood flow network can limit your rate of muscle gain. Somy general rule of thumb is to always include cardio in your week or periodize in and out of your life, but never neglect it for too long and never overdo it.

Any amount of formal cardio below the time devoted to lifting can likely still maximize your gains. Men can lean on the higher end of cardio compared to women because female physiology is naturally more endurance based. They have fantastic work capacity and recovery capabilities.

Don’t believe me? Train with a girl of similar training experience. You’ll be winded between sets of squats and deadlifts while she can start a new set minutes sooner. In fact, from my experience, many women can maintain excellent aerobic capacity without any formal cardio. Ironically though, women tend to gravitate towards doing more of it while men avoid it.

But regardless of sex, many people still find cardio enjoyable, so feel free to include it in your program. It’s encouraged and shouldn’t compromise your gains unless you do an excessive amount.

Calvin Huynh
Calvin Huynh is a trainer, online coach, writer, and joyful ruler behind His content has reached various top sites and he has worked with a variety of clients ranging from top CEOs, hardcore lifters, everyday desk workers, and stay at home moms. When he’s not working, he spends his time going to church, dreaming of unicorns, and eating whole pints of ice cream on a comfortable couch somewhere in Southern California.