Does Cardio Kill Gains?

Forget the ‘F word,’ bodybuilders fear the ‘C word!’

“I didn’t sign up for this.” That’s the attitude many if not most bodybuilders have about cardiovascular training.  We embarked on this journey of muscle-building to pump iron, to hear the clang of heavy weights, and challenge ourselves to lift more and more weight over time as our bodies transformed and became more massive. Aerobics or spin classes were never part of the plan, and neither was toiling away on treadmills, bikes, and stairs that went nowhere. But the main reason most bodybuilders avoid cardio like a COVID-positive babe who wants to make out is out of the sheer terror that it will kill our gains. We work much too hard with the weights and being dedicated to a solid nutrition and supplementation plan to let cardio wreck it all. Is it true though? Will cardio keep you from growing? Could it even cause you to lose precious size and strength? The answer isn’t a simple yes or no, but by the time you finish this you will know how to incorporate cardio into your program so that it helps, not hinders your muscle growth.

NEVER do cardio before weights

I’ve never ceased to be amazed at how many people never consider that performing cardio before your weight training will diminish your performance with the weights, but your cardio performance – at least in terms of the type of cardio bodybuilders tend to do – will not suffer if you do it post-workout. You only have so much energy and muscle glycogen to draw on for any given workout session. If you hit the Stepmill for 30 minutes before training legs, there is no way you can have the same quality leg workout as you would working them fresh or after a very brief cardio warm-up of 5-7 minutes. Studies have shown that high-intensity cardio can impair performance with weights for up to 6 hours, which is why many bodybuilders do cardio first thing in the morning and return to hit the weights in the late afternoon. Since a lot of us don’t have time to do two exercise sessions a day, your best bet is to do your cardio after your weights, or on days you don’t train with weights at all.

Who should never do cardio?

I do feel there is a specific population that should probably never do cardio, and those are the true ‘hardgainers.’ Before you put your hand up crying out, ‘that’s me!’ very few people truly fit into this category. They tend to be under the age of 25, with the classic ectomorph features: thin-boned, with a turbo-charged metabolism that incinerates everything they eat. These are the type of guys you watch put down disgusting amounts of food any time you’re out to eat, yet they remain thin and lean. For the real hardgainers out there, adding any amount of lean muscle tissue is an uphill battle, and anything that burns calories aside from weight training must be avoided at all costs. Cardiovascular training would work against their mission to remain in a caloric surplus and eke out what gains they can. 

Avoid very intense cardio with high resistance

All forms and styles of cardio are not equal. Intensity can range from an easy strolling pace on a flat treadmill to HIIT-style all-out bursts of effort in wind sprints, stair climbing, or a spin bike. If your legs get pumped from your cardio sessions, or worse, sore the next day as if you’d trained legs, you need to scale back the intensity. You don’t want to incur any muscle damage from cardio, or else you have crossed over from aerobic into anaerobic training. We all have different fitness levels, but it’s safe to say that sprinting up a highly-angled treadmill is not going go compliment your leg workouts – instead it will probably give them extra work that your legs won’t be able to recover and grow from.

While there are many arguments in favor of the effectiveness of HIIT cardio, or alternating periods of sprints and recovery at a moderate pace, most bodybuilders prefer steady-state cardio to burn fat without risk of muscle loss. That means warming up and finding the proper pace to follow for the duration of the session. Using the old formula of ‘target heart rate,’ you can easily arrive at that pace using the sensors on almost every cardio machine. Your maximum heart rate is 220 minus your age. If you’re 25 years old, that’s 195. The optimal fat-burning zone is 70% of that, or 136.5 beats per minute.

Don’t overdo cardio

It’s doubtful that many of you need to hear this, but excessive cardiovascular training will indeed curtail gains in muscle size and strength. How do we define ‘excessive?’ It won’t look the same for everyone. Just about everyone aside from the aforementioned genuine hardgainers seems to do fine with 3-4 sessions of 20-30 minutes a week. Nobody can get away with hours of cardio every day and continue to grow.

Our bodies have an amazing capability to adapt, but they can’t adapt to diametrically opposed goals at the same time. Even with running, you can’t be a great sprinter and also a top marathon runner.  The training for each type is very different, as are the adaptations the body makes to improve at each. Doing hours of cardio every day will not allow your body to recover and grow from your weight training. You will need to find your own sweet spot, but most bodybuilders seem to notice a negative impact on their strength and muscle mass once they exceed 40-45 minutes of cardio, 4-5 times per week. And by negative, I mean they start getting weaker and smaller. Sounds bad, and it is!

How cardio can boost your gains

We typically think about our weight training in terms of short bursts of intense effort, and to a point that’s accurate. Strength training fits that description to a T. Once we get into higher rep ranges for hypertrophy (see article “The Best Hypertrophy Program” by Randy Reith), the sets do take longer to complete. That’s where you need endurance to perform at your best and reap optimal results.

Some of you are rolling your eyes because you’ve been conditioned to think 8-10 reps is the ideal range for all exercises, but I guarantee you that legs in particular will never reach their full size potential if one adheres strictly to that number. Instead, they thrive on the inclusion of higher-rep sets in the realm of 15-20 or more reps. Squatting for higher reps is one of the most physically demanding things you will ever do with weights. It takes far more effort and determination to grit through 315 for 20 than it does 405 for 5.

In particular, it’s your ‘wind’ that typically gives out before your thighs are fully exhausted. By the time you get to reps 14-15, your lungs feel like they’re bursting out of your torso and it’s a real struggle to take in adequate oxygen. For those of you who eschew all cardiovascular training, it’s safe to say that you will have to quit any productive high-rep set of squats, hack squats, or leg presses long before your quadriceps have been fully taxed. This is where the benefits of cardio really become evident.

If you’ve performed cardio at even 3-4 sessions a week, you will be able to bust right on through that set and take your quads all the way to their limit without your capacity to take in adequate oxygen being a limiting factor. Need more convincing? Several studies have shows that moderate amounts of cycling plus weights produced greater muscle growth than weights alone. Why? The answer could lie in the ability of cardio to improve circulation, heart, and lung function.

How about your health?

On that note, ask yourself this question. What good is having a rocking buffed body on the outside if you’re not healthy inside? Here’s a fact you may already know: heart disease is still the number-one cause of death in the USA, claiming nearly 700,000 lives every year. Weight training is the best method to strengthen your muscles and maintain bone density, but it doesn’t do much for your heart and lungs. Only cardiovascular training can strengthen those as well as keep all your blood vessels open so the blood can travel freely throughout your body with no narrowing or blockage of the veins and arteries. So if you want to be able to enjoy that muscular body in good healthy for many years to come, it would behoove you to include cardio training in your regimen along with weights.

The bottom line

For all but a few of you out there with volcanic metabolisms, a moderate amount of cardio will not impede your gains. It will actually help you if used correctly. Don’t do cardio before your weight training workout, don’t do extreme amounts or at very high intensity, and you have absolutely nothing to worry about. Cardio will only kill gains if abused. Done properly, cardio will make you a better bodybuilder.

Devin Dalton

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