Ask any “expert” when it is best to incorporate cardio into your workout and you are sure to get answers ranging from “Do your cardio first to warm up” to “Never do cardio before leg day.” And of course there’s this: “Cardio kills your gains.”
However, the myth that cardio ruins your gains needs to go. Improving your cardiovascular health improves recovery, reduces stress and keeps you above ground longer.
For years, lifters worried that a few miles of running on the treadmill or a HIIT session after lifting would shred their hard-earned muscle. And while poor cardio timing can hinder your progress, properly programmed cardio can complement it.
Here we’ll debunk the science, debunk the fear, and show you when cardio helps, when it hurts, and how to structure it based on your goals.
Origin of the cardiomyth
The idea that cardio kills your muscle growth didn’t come from the lab, it came from the gym bros.
Old-school bodybuilders considered cardio the enemy. It’s hard to argue with a muscular man who believes that more than five reps is considered cardio. At the time, the message was clear: if building muscle is the goal, cardio is a waste of time. Cardio was only something you had to go through to lean forward quickly during a cutting phase.
The way endurance athletes looked only enhanced the contrast. Lifters saw that look and thought, “Is that what cardio does? No thanks.”
This mentality became even more pronounced in the early 2000s, when fitness culture split into two distinct groups: cardio bunnies who didn’t want to get fat and lifters who did. Then influencers and gym bros added fuel to that fire, dismissing steady-state cardio and warning everyone that it will ruin your gains.
That fear lingered, and what was lost in all the noise? Context.
Now it’s time to give some.
How Cardio Really Helps Your Profits
Cardio isn’t the bad guy in your quest to build muscle. When programmed and executed properly, it is a tool that supports fat loss, improves recovery and increases your work capacity.
Here are three great reasons to combine cardio with lifting.
Fat loss and conditioning
If your main goal is to lose fat while maintaining muscle, cardio can be your ally, but it’s all about timing and intensity. Doing cardio after lifting, when glycogen stores are low, can boost your fat-burning efforts. A 2015 study in sports medicine found that combining resistance training with cardio after lifting improved body composition more than resistance training alone – without negatively affecting strength.
LISS: low impact, high return
Low-Intensity Steady-State (LISS) cardio, such as incline walking, cycling or light rowing, has little impact on strength or hypertrophy. It aids recovery by increasing blood flow to sore muscles, reducing stress and improving sleep.
Heart wins are still wins
Better cardio equals better work capacity. That means you can recover faster between sets, train harder during workouts, and keep your engine humming for longer. That’s not a “loss of gain” – that’s optimizing it.
Cardio timing really matters
Like many myths, there is a bit of truth hidden underneath. Cardio doesn’t automatically destroy gains, but it’s all about the timing.
High-intensity cardio before lifting? Not ideal
If you jump straight into sprints, hill intervals or a long distance run before lifting, you’ll start your lift feeling tired. That’s a problem, especially for compound lifts that require maximum effort.
This is why:
- Your central nervous system is not as sharp.
- Muscle glycogen is partially depleted.
- Power output and lifting technique suffer, especially in lifts that require explosiveness and stability. A 2016 Journal of Sports Sciences study found that doing cardio before strength training reduces strength performance.
The interference effect is real
The ‘interference effect’ describes the competing adaptations that occur when endurance and strength training are not effectively combined. A extensive review JSCR showed that concurrent training can inhibit hypertrophy and strength development, especially when the modalities are performed back-to-back at high frequency and with poor sequencing.
It’s not about avoiding cardio, it’s about putting it where it fits. Before strength training, this can compromise performance. It then becomes a tool for recovery, conditioning and body composition.
Targeted cardio timing
So, when are the best times to do your cardio? The best time to do cardio clearly depends on your training goal. Here’s how to make it work for you.
For fat loss:
- When to do it: After lifting, or in separate sessions.
- Why: You have already used your glycogen during strength training. Now you can really tap into the fat and glycogen stores, depending on whether you do HITT or LISS.
- Bonus: Fasting in the morning on days off can increase the deficit, if recovery is good.
For muscles:
- When to do it: After weight lifting or on rest days.
- Why: Your energy should go towards muscle growth. Don’t deflate your central nervous system with high-intensity cardio first.
- Tip: 1 to 2 short LISS sessions per week are usually sufficient to maintain fitness when maximum muscle strength is the goal.
For endurance:
- When to do it: Prioritize cardio sessions and do strength training after or on alternate days.
- Why: Your performance depends on aerobic performance: lifting to support endurance and reduce the risk of injury
This is what happens when you believe cardio eats away at your gains
Thinking that cardio automatically cancels out strength gains has consequences. Here’s how this myth causes problems with progress:
Lifters avoid cardio altogether
Many strength-oriented lifters eliminate cardio for fear that it will “steal” their gains. But skipping conditioning means they’re missing out on the cardiovascular health, recovery benefits and work capacity that actually support better lifting – feeling strong but out of breath after a single kick? Those are not achievements; that’s your heart telling you to do cardio.
Encourages a false either/or mentality
This myth promotes a black and white view: either you are a “cardio person” or a “strength person.” That is limiting. A balanced training plan can and should include both, if timed and programmed properly. Lifters who believe in the myth are missing out on the benefits of becoming well-rounded athletes.
Miss out on health and recovery benefits
Cardio isn’t just about burning fat. It improves heart health, circulation, blood pressure and metabolic flexibility – key pillars for long-term performance and well-being. When you neglect cardio, these benefits diminish. Additionally, low-intensity cardio, such as walking or cycling, supports active recovery by increasing blood flow to sore muscles, clearing waste products and delivering nutrients. This leads to better recovery between lifting sessions.
Blocks fat loss and conditioning
Strength training alone often does not provide enough of a metabolic boost to promote fat loss, especially in experienced lifters. Without some form of steady-state or interval-based cardio, your body has fewer tools to efficiently burn calories and adapt to longer duration workouts due to a lack of aerobic endurance. This lack of endurance becomes apparent during the cutting phases, when cardio is crucial for maintaining a calorie deficit without losing lean body mass.
The last takeaway
Cardio won’t wipe out your gains, but poor planning can. The myth that cardio and lifting can’t coexist is like saying you can’t eat carbs and still get lean. It’s not about one or the other. It’s about smart sequencing.
If strength, size, or power is your main priority, lift first. Then your nervous system is sharp, your muscles are fresh and your performance is at its highest. Cardio can come later, at the end of your session, or on separate days, depending on the intensity. On the other hand, if you’re training for endurance or working toward a race, prioritize cardio first and treat your lifts as a performance support.
Cardio is not your enemy; it is your ally if you use it at the right time and in the right way.
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