Does Cardio Really Kill Your Gains?

Has bro culture been telling the truth this whole time?

Published January 17, 2023

·

Updated March 29, 2023

If you take your fitness advice from your local gym bro, you’ve probably heard the notion that even looking at a cardio machine can make your hard-earned muscle gains disappear overnight. While that’s certainly not the case, there is some merit to the myth. Multiple studies exist, both supporting and negating the perceived effects of cardiovascular training on strength progress. All this conflicting information can certainly leave you in a tailspin when it comes to planning out your weekly regimens.

Now, this isn’t to say there aren’t benefits to training for cardiovascular improvement. Many athletes can still achieve a proper health and wellness routine through aerobic exercise. The confusion pops up, however, when you start to mix in cardio with more anaerobic modalities.

So, does cardio affect muscular development? It’s not as cut and dry as many would like it to be. The best answer, naturally, all lies in how you structure your training, what your intended goals are and how you view each discipline. Below are some answers outlining how this myth came to be, as well as some tips on how to most efficiently add cardio training to your normal strength regimens.

sweaty athletic man feeling tired on sports training in a gym

How Cardio Can Influence Your Strength Totals

It can compromise cell pathways.

One of the most scientific ways to showcase how cardio may derail your muscle growth is by looking at the cell pathways that power your adapting physique. The body has two pathways for cell metabolism and growth: the mTOR pathway and the AMPK pathway. While the mTOR pathway is more active during anaerobic exercises like lifting or other resistance training modalities, the AMPK pathway is more in-line with aerobic training, i.e., cardio. Activating both pathways back-to-back could result in less protein synthesis in the mTOR route, which in turn can lead to less muscle growth.

It’s going to tire you out.

When thinking about combining cardio and strength-based training, you need to essentially think of these as two separate workouts. And what do you think you’ll feel after tackling two consecutive sessions? Fatigue, of course.

Kicking off a workout with a treadmill run or extended cycling session can leave you feeling more tired and spent when it comes to those scheduled lifts, giving off the perception that your less intense training is the result of cardio. The same effects can be felt if you perform a cardio session after your prescribed strength workouts, putting your frame under more intensity and thus requiring more recovery time outside the gym. When it comes time to return to the gym, your body could still be feeling the results of yesterday’s double-dip. This tiredness can leave many athletes hesitant to combine the two disciplines, instead opting to choose one or the other rather than fine-tuning their regimens for better results (more on that later).

There’s less time for protein synthesis.

We all know that muscle growth is not just a result of in-gym performance. You need to match your training efforts with a thoughtful, effective nutrition plan, too, if you want to see those monster gains. One of the most efficient ways to ensure your body is fueling up properly is by giving it the nutrients it needs at the right times, mainly after a hard-fought strength training session. While there are debates surrounding when this “anabolic window” is, a good rule of thumb is to try and get something in your system roughly 30–45 minutes after anaerobic training. Adding a secondary cardio workout post-lift doesn’t exactly help you meet that deadline now, does it?

Despite these potential blockers, there are still plenty of benefits to tackling both cardio and strength training in your overall fitness journey. Blood pressure and cholesterol improvement, blood vessel health and others are just a handful of perks that can come with proper scheduling, yet why are so many late on the drop to configuring their schedules for both disciplines? Like your trusty credit card, though, it’s all a matter of how you use it.

How to Efficiently Combine Cardio and Strength Training

Space out your workouts.

Regardless of where your focus lies, it’s best to separate your cardio and strength training whenever possible. After all, your body needs time to recover if you want to maximize your output whether pacing toward a new best time or chasing down that hefty squat total. Look to space out your cardio and lifting sessions on different days, as this can help alleviate any extended fatigue while still giving your sessions that always-appreciated variety.

Plan your sessions accordingly.

I get it, not everyone’s schedules can accommodate multiple modalities throughout the week, but if you must get both your aerobic and anaerobic exercises in on the same day, bring some proper planning to your timeline. Avoid signing up for extended cardio sessions when you know you’re about to embark on an intense muscle-sculpting session. This means forgoing any multi-mile excursions or runs lasting over 60 minutes. Also, you’re better off timing your cardio for after your lifts, as this can keep your energy more focused on resistance training. Think about it, where do you want your energy most — that PR deadlift or that mile-long jog atop the treadmill?

Prioritize low-impact modalities.

When looking to combine both cardio and strength training, not every exercise is entirely plug and play. If you want to get the most out of both modalities, look for less impactful exercises like rowing or cycling as opposed to, say, running on a treadmill. Running in itself can be as high-impact as your load-bearing bench sessions, thanks to the force and stress placed on your joints in each stride. Combining this with strength training can often leave your body drained and unable to recover properly before the next regimen. Instead, look for cardio routines that will put less of a strain on these hinges. These modalities can even add to your overall anaerobic routine, working multiple muscle groups while still providing that desired cardio burn. If you must run, try to keep your mileage to a minimum and give your knees some impact resistance by jogging in a pair of well-cushioned sneakers.

Cardio and strength training aren’t mortal enemies when it comes to building the ideal fitness routine. Take these tips into consideration and dispel those archaic mantras today.

How-To’s & Explainers, Running, Top Stories, Training & Recovery