Cardio causes a different type of adaptation from hypertrophy training. Instead of stimulating muscle growth, cardio causes us to develop more blood vessels, gain additional mitochondria in our cells, and it even increases the size of our hearts. Make no mistake, these are all great adaptations. But they aren’t muscle gains.
If you want to increase the size of your muscles, no amount of cardio will help. Cardio simply doesn’t stimulate any muscle growth. So if we’re trying to build muscle, we need to focus on hypertrophy training, which is usually done by lifting weights.
But what if we lift weights and do cardio? Most people know that cardio doesn’t stimulate muscle growth, so this article is written for skinny guys who are considering lifting weights and doing cardio.
Doing both hypertrophy training and cardio causes us to adapt in two separate, competing ways. We get something called an interference effect, which can reduce muscle growth. That’s what people say, anyway. Is that true?
Things get even more confusing because we’re naturally skinny “ectomorphs.” The more cardio we do, the more calories we’ll burn, and the more calories we’ll need to eat. For us, even just thinking about cardio burns too many calories. If you think that’s bad, though, imagine needing to write about it. I can already feel my metabolism rising. I’m going to have to eat so much trail mix after this.
- The Benefits of Cardio
- Should You Do Cardio While Bulking?
- Will Doing Cardio Make it Harder to Gain Weight?
- Will Cardio Kill Your Gains?
- Can Cardio Make Your Gains Leaner?
- Does HIIT Pair Best With Bulking?
- What Type of Cardio Goes Best With Lifting?
- Should You Do Cardio Before or After Lifting?
- Should You Do Your Cardio Fasted?
- Key Takeaways
The Benefits of Cardio
Cardio stands for cardiorespiratory training, where the goal is to elevate our heart rate in order to improve our cardiovascular fitness. It’s a catch-all term for activities designed to strengthen our hearts and lungs—jogging, rowing, biking, aerobics, and so on.
Cardio is an important part of general fitness. In fact, cardio is pretty much synonymous with general fitness. With good reason, too. There are many benefits to cardio (study):
Cardio burns calories and helps people lose weight.
- It makes our hearts bigger and more efficient.
- It increases our lung capacity.
- It helps to reduce our risk of heart disease.
- It improves mood and reduces anxiety.
- It can improve sleep.
One of those purported benefits is kind of scary. Most of us ectomorphs already have a hard time eating enough to gain weight. The last thing we need is a type of exercise that burns more calories, raises our metabolisms even higher, and doesn’t increase our appetites by a proportionate amount. So I’ve crossed that “benefit” out. (I would have fully redacted it, but our blog doesn’t have that feature.)
The rest of the benefits are pretty rad, though, even for skinny guys. It would be a real shame to avoid cardio simply because we struggle with calories.
However, cardio isn’t really going to make us look any better. It won’t make us stronger, either. And it certainly won’t help us bulk up.
For that, we need to lift. Most of us already know that. So let’s just assume that we’re lifting and that we’re considering doing cardio in addition to lifting.
Should You Do Cardio While Bulking?
The short answer is yes. Most health institutions, including the World Health Organization, recommend doing at least 150 minutes of cardio and at least two strength training workouts each week just for the sake of being generally healthy. That applies to everyone, including us naturally skinny guys.
Lifting and cardio provoke completely different types of adaptations, both of which are important. We should do both.
The longer answer is that it depends. In our case, one of the main benefits of cardio—weight loss—has the potential to harm us. So it isn’t as clear-cut as it is for someone who’s overweight. We need to make sure that the cardio we’re doing isn’t keeping us underweight.
Furthermore, you don’t need to improve every aspect of your lifestyle all at once. If you’re totally sedentary and your main goal is to build muscle, you could start by spending a few months bulking up, focusing on gaining 20–30 pounds of muscle. Once you’ve bulked up and your lifting habits have grown as strong as your muscles, that’s a perfect time to add in some cardio for even more general health benefits.
Now, you don’t necessarily need to add in dedicated cardio. Brisk walking can technically count as cardio, as can some forms of resistance training.
Lifting Can Count as Cardio (Sort Of)
A 2014 study published in the Journal of Exercise Science (study) evaluated a bodybuilding workout by cardio standards. They measured the heart rate of sixteen people while doing a typical bulking workout consisting of the bench press, lat pulldown, biceps curl, leg press, and so on. They did three sets of ten reps for each exercise. Again, fairly standard.
The researchers found that for about half of every bulking workout, the participants had the ideal heart rate for improving cardiovascular fitness.
This wasn’t in the study, but I’d also argue that if we wanted even greater cardiovascular benefits, we could structure our bulking workouts in a way that would keep our heart rates higher throughout. And, in fact, this is how we generally recommend training.
One way that we do this is by using modified circuits. In order to build muscle properly, we can benefit from giving our muscles plenty of rest time between sets. However, while a certain muscle group rests, we can lift with a different muscle group. For example, we can do a set of squats, rest a minute as our heart rate settles a little bit, then do a set of chin-ups, and then rest another minute before returning to the squats. That way we’re keeping our heart rates fairly high throughout our workouts, but we’re still giving our muscles at least two minutes of rest between each set.
That’s going to allow us to build muscle at full speed while also getting the benefits of doing more cardio. It still won’t be as ideal as a dedicated cardio routine, but it’s getting closer.
Anyway, if we’re doing bulking workouts, we can count at least half of our time lifting weights as cardio training. So an hourlong workout would count for 30 minutes of cardio. If we lift three times per week for an hour each workout, that’s already 90 minutes of cardio. That’s more than enough to help a sedentary person improve their cardiovascular fitness as they build muscle.
Then, when you’re ready to increase the amount of cardio in your routine, you could add in a brisk walk for an hour on the weekend or toss in a couple of 30-minute cardio sessions during the week. That will get you to the 150-minute cardio target.
Similarly, when we hear a recommendation to do “strength training,” that doesn’t mean that we need to do low-rep powerlifting-style workouts. That style of training isn’t as good for building muscle or improving our cardiovascular health. And besides, that’s not what health organizations mean anyway. They simply mean lifting weights in a way that will make us stronger, improve our bone density, and put some heavy loading on our spine. A good bulking workout will accomplish all of that.
Will Doing Cardio Make it Harder to Gain Weight?
Yes, doing cardio can make it harder to gain weight. One of the main effects of cardio is that it burns calories without causing a proportional increase in appetite (study, study). So if we burn 500 calories while jogging, we might only want to eat an extra 300 calories, leaving us in a calorie deficit of 200 calories. This is why cardio tends to cause weight loss.
For the average person, that might not be a big deal. In fact, having an excuse to eat more calories might seem like a blessing. But for us naturally skinny guys, that’s a nightmare. Most of us already struggle to eat enough calories to gain weight.
We struggled with that ourselves, and so over the years, we’ve become masters of helping skinny guys eat more calories. But it’s still hard. And the more cardio we do, the more calories we’ll burn, and the harder it will be to gain weight.
So, yes, the more cardio you do, the harder it will be to gain weight. And if you can’t gain weight, you won’t be able to build an appreciable amount of muscle. Your bulk will grind to a halt. This is how cardio can kill gains.
Does that mean that ectomorphs should avoid cardio while bulking? So, first of all, there’s a difference between your daily lifestyle and bulking. Doing cardio is part of a healthy lifestyle, so in general, you should certainly try and do some. If you’re going through a bulking phase, though, the question becomes harder to answer. It really depends.
To be fully honest with you, cardio was the last thing I was thinking about while bulking up. I was way more concerned about building muscle than I was about my longterm health. It was only once I solved my skinniness that I started caring about these longer-term health goals. So I won’t fault you if you don’t want to think about this just yet.
Still, there’s no getting around the fact that cardio is good for our health. Technically speaking, we should do cardio, even as skinny guys, and even while bulking. But if it’s too hard to eat enough calories, you may want to take a break from it for a few months as you bulk up.
On the other hand, if your digestive system can handle some extra trail mix, and you’ve got the time and energy for it, then I’d definitely recommend doing cardio while you bulk up, even if you’re quite skinny. There are a few good reasons for doing cardio while bulking, some of which we’ve already covered, and some of which are still to come.
Will Cardio Kill Your Gains?
Technically speaking, yes, cardio could kill your gains. Even if you can manage to eat enough calories to gain weight, you’ll run into something called the interference effect. Essentially, if you train for a marathon and a powerlifting meet at the same time, those signals will start to cancel each other out. After all, you’re training for extreme endurance and extreme strength. You’re training for adaptations that are at opposite ends of the strength-endurance continuum.
Some studies show that your endurance and strength gains would each be reduced by 20-30% if you’re training for both goals at once (study). That’s not ideal, no, but it’s nothing to be scared of, either. You’ll still get 70–80% of the strength and endurance. That’s still fantastic progress towards two worthy goals.
Practically speaking, no, cardio won’t noticeably reduce muscle growth—at least not in the way you care about. Most people forget that most of the adaptations that we make are location-specific.
So if you’re training for a marathon, it’s your legs that are going to develop better muscular endurance. That’s going to make it a little bit harder to bulk up your legs, sure. And maybe your squat strength doesn’t climb quite as high. But you’ll still be able to build just as much muscle in your upper body (so long as you aren’t struggling with overall fatigue).
Since most guys are mainly interested in bulking up their upper bodies, that’s not a bad way to bulk up. You’ll have versatile legs, a strong heart, and a muscular upper body.
Furthermore, you probably aren’t doing marathon and powerlifting training. That’s the most extreme example, which is why it was studied. The researchers figured that if anything could produce an interference effect, it would be extreme strength competing against extreme endurance.
Chances are, if you’re trying to bulk up in a healthy way, you’re probably doing hypertrophy training and then adding in a bit of cardio to improve your health (or because you enjoy it).
Hypertrophy training is already in the middle of the strength-endurance continuum. And you probably aren’t combining it with extreme endurance training, either. If you play some casual sports or do some martial arts, biking, jogging, or yoga, that’s not really going to interfere with bulking.
How to Prevent Unnecessary Casualties
When mixing cardio into a bulking routine, just make sure that you aren’t totally killing yourself in the gym. Don’t lift to failure, don’t do multi-hour workouts, don’t train six days per week. None of those things will reliably speed up muscle growth, but they will make it much harder to recover from your training. If you’re doing a ton of cardio in addition to that, you might wind up totally crushed by the workload.
My main point here is that the interference effect won’t noticeably reduce your ability to build muscle. I wouldn’t worry about it. The main problem with adding cardio into a bulking routine is that it’s going to make it harder to gain weight. It can be a pure calorie issue. That can kill a skinny guy’s gains.
Can Cardio Make Your Gains Leaner?
Doing cardio could conceivably make your gains leaner, yes. There’s an idea called energy flux (G-Flux). Ryan Andrews, RD, and John Berardi, PhD, are famous for writing about it over on Precision Nutrition. We’ve written about it in our article for skinny-fat guys, too.
With g-flux, the idea is that the more calories you burn, the more calories you’ll need to eat, and so the more nutrients you’ll be able to get into your system. That means more vitamins, minerals, antioxidants, probiotics, fibre, and phytonutrients. And since your overall food volume is higher, you don’t need to worry as much about making every calorie count. It allows you to eat a more flexible bulking diet while still getting all of the nutrients that you need.
Furthermore, the extra activity that you’re doing will improve your general fitness, make it easier to burn visceral fat, and speed up your recovery between workouts. Because you’ll be generally fitter, you’ll be in better shape to bulk up.
This means that cardio could help you build muscle more leanly simply because you’ll be in better shape, you’ll be getting more nutrients out of your diet, and you’ll be recovering more smoothly from your bulking workouts. This is going to facilitate muscle growth, leaving fewer resources available to be stored as fat. Put simply, bulking is easier when you’re in great shape.
How strong is this effect, though? Can cardio make your gains noticeably leaner? It’s unclear.
If you’re already lean and skinny with a fast metabolism, you probably don’t need dedicated cardio in order to keep your gains lean. Furthermore, trying to raise your g-flux is just going to make it harder to get into a calorie surplus, so it might get you into more trouble than it’s worth.
Personally, I’ve always had a high metabolism. I’ve never intentionally done cardio while bulking. The closest I’ll come to doing cardio is walking to the grocery store and carrying my groceries home. Or, more recently, going on a 20-minute walk every evening while carrying my son around in my arms.
If you’re sedentary and you’re a beginner lifter, you can probably gain muscle quite leanly with or without cardio. Beginners have such a strong response to lifting weights that cardio simply isn’t needed in order to make lean gains, especially for us naturally skinny guys.
However, if you’ve got more of a skinny-fat look even after lifting weights, then you might want to consider intentionally doing some cardio while bulking up. Some skinny guys store fat more easily. There are a variety of reasons for that, ranging from genetics to daily activity levels to how well you sleep. If you naturally have a higher body-fat percentage, adding in some cardio (or just moving more in general) is often a good way for skinny-fat guys to make leaner gains.
(Keep in mind that doing cardio can help you become leaner, but it won’t necessarily help you build bigger abs. Some ectomorphs have skinny abs, which means that you might also need to intentionally bulk up your ab muscles before you have good ab definition.)
But again, regardless of your situation, if cardio is making it impossible to eat enough calories, just save it for later. You can always add in some cardio after you’ve finished bulking up. Or perhaps after you’ve gotten your newbie gains, at which point your muscle gains will slow.
Does HIIT Pair Best With Bulking?
The next question we get is about what type of cardio to do while bulking. Generally, we recommend doing easy types of cardio that you enjoy, don’t leave you feeling fatigued, and don’t bang you up.
Remember, we’re skinny guys who are trying to bulk up. We don’t need the cardio right now, and we damn well don’t want to destroy ourselves with it.
Some people swear by it, but most sane people hate using HIIT to improve their cardio. It’s quick and efficient, yes, but so is eating a scorpion pepper. That doesn’t mean that everyone is going to enjoy that short vacation in Hell.
When it comes to HIIT, I hate to sound like a wimp, but it really sucks, man. If you’re doing it properly, you’ll certainly hate being alive, and you might throw up, too. Even just in terms of compliance, it can take a lot of willpower to psyche yourself up for the intense pain. Most people do it for a few weeks and then find some sort of excuse to stop.
And besides, lifting weights is a form of HIIT anyway. You lift weights intensely for 5–20 reps, rest for a couple of minutes, then do another intense 5–20 reps. The difference is that lifting isn’t designed to stress your cardiovascular system anywhere near as intensely, so it doesn’t tend to suck. I mean, taking a 20-rep set of squats to failure would certainly suck, but most bulking programs wouldn’t ask you to do that.
There are some interesting pros and cons to HIIT, though. On the one hand, because it’s so intense, HIIT has a greater chance of interfering with your bulking workouts. Bike sprints are more likely to fatigue your legs than going on a brisk walk. But then on the other hand, because it’s so intense, HIIT can stimulate a bit of muscle growth in and of itself. So in the end, it will probably balance out.
The bigger worry with HIIT is that you might get injured, become too fatigued to lift properly, or you might hate it so much that you give up on your routine as soon as life gets stressful or busy. If your workouts always require a ton of willpower, they won’t be sustainable.
Anyway, if you like high-intensity interval training (HIIT), and if you’re good at it, then you’re crazy, but feel free to keep being crazy. It’s going to be great for your health.
But if you aren’t already in the habit of doing HIIT, I’d recommend easing into cardio with an easier variation. Hopping on a stationary bike, going on brisk walks, doing some swimming, or just being more physically active in general tends to be an easier type of cardio to add into a bulking routine.
What Type of Cardio Goes Best With Lifting?
The first thing we need to consider is the intensity of the cardio. There are a number of different style of cardio, ranging from jogging (LISS) to bike sprints (HIIT) all the way to CrossFit (HIPT).
- Low-Intensity Steady State: LISS is the most traditional type of cardio, so most of the benefits you associate with cardio are most strongly associated with LISS. For example, this is the type of exercise that’s best for improving the efficiency of our hearts. This style of cardio is also the most different from weight training.
- High-Intensity Interval Training: HIIT is a more modern form of cardio that’s touted as being a far more efficient, albeit painful, way to train. Weight training is also a form of HIIT, but when a routine is designed to promote cardiovascular adaptations, the emphasis is shifted to keeping our heart rate high, which makes a HIIT routine much better for improving cardiovascular fitness.
- High-Intensity Power Training: HIPT programs, such as CrossFit, as sort of a blend of traditional weight training with modern cardio HIIT routines. They’re perfectly good for making small improvements in muscle mass and strength while making great improvements in cardiovascular fitness, and that versatility makes it great for many people. However, HIPT isn’t very good for bulking up, and it combines quite poorly with hypertrophy routines.
Of these different styles of cardio, I think traditional cardio combined with weightlifting is the most powerful way to improve our health and overall performance. However, there are some instances where HIIT can outperform traditional cardio, such as when doing both cardio and lifting in the same workout (which we’ll cover in a few seconds).
If we look at the research, we see that traditional cardio combined with hypertrophy training seems to produce the most muscle growth, too, although the differences aren’t major.
The second thing we need to consider is what type of exercise we should do to get our heart rate up. We can bring our heart rate up by jogging, biking, swimming, rowing, doing weight training circuits, and so on.
These different forms of cardio have slightly different effects on us (study):
- Weight training circuits: Weight training circuits might seem like they’d be the best for stimulating muscle growth, and that’s true, but we’re already doing a hypertrophy program. Furthermore, this style of cardio overlaps so heavily with our bulking workouts that it’s the most likely to produce an interference-effect.
- Jogging: Jogging is great for our cardiovascular health and produces a unique set of adaptations from lifting weights. However, unless you’re quite good at running, it can be pretty hard on our joints and connective tissues. You also need to catch your body weight on one leg with every stride, which can cause quite a lot of muscle damage. It’s not always an easy form of cardio to recover from. As a result, it’s usually not appropriate for beginners.
- Biking: biking, especially if you’re using a stationary bike, produces the same beneficial adaptations as jogging, but without stressing your joints and without causing much muscle damage. This makes it incredibly easy to recover from. It also stresses just the lower body, meaning that it won’t interfere whatsoever with your upper-body size or strength gains.
- Ellipticals, rowing, and so on: there are other styles of cardio that are fairly easy on our joints and fairly easy to recover from. However, many of them have an upper-body component. If you’re keen on building a bigger upper body, it’s usually better to do your cardio with your lower body. It’s not a big deal, mind you.
- Walking: going on brisk walks can actually be a fairly effective form of cardio. It’s not efficient, but it’s easy, it’s healthy, it’s low-impact, and it’s a breeze to recover from. Of all the types of cardio, this is my personal favourite.
The most important thing is choosing a form of cardio that you enjoy and that makes you feel good. However, if you have no preference, I think hypertrophy training combines the best with traditional cardio instead of HIIT, and I’d argue that walking and stationary biking are the best ways to do it.
Should You Do Cardio Before or After Lifting?
If you’ve decided to add cardio into your lifting routine, the next question is when you should do your cardio. Should you do it before lifting weights, after lifting weights, or keep it entirely separate?
The concern with doing your cardio before lifting weights is that it will make you tired. If you hop on a stationary bike for some HIIT or go for a jog on a treadmill, it’s going to be harder to do your squats and deadlifts afterwards.
The problem with doing your cardio after lifting weights, though, is that you might cancel out some of the growth that you’ve worked so hard to stimulate. Lifting weights tells your body that you want to become bigger and stronger, great. Then you hop over to the treadmill to do your cardio, and your body thinks you’ve changed your mind—it scales back the muscle growth to focus on improving your cardiovascular health instead.
How does this play out in the research? One study that looked into combining cardio with weight training found that guys gained strength just fine if they did their cardio after their strength training. However, muscle growth is a whole separate story. The researchers found that doing cardio after lifting cut muscle hypertrophy nearly in half.
So for muscle growth, we definitely don’t want to be doing traditional cardio after lifting. Much better to do our cardio beforehand, or, even better, on a whole separate day.
However, keep in mind that not all cardio is the same. HIIT produces a very different set of adaptations from steady-state cardio. I’m personally of the opinion that since lifting is a form of HIIT, we’ll get better overall adaptations by doing both lifting (HIIT) and traditional cardio (LISS). However, if you’re trying to do both lifting and cardio in the same workout session, perhaps it’s better to combine your lifting with a HIIT cardio routine. Because the adaptations they produce are more similar, they’ll be less likely to produce an interference-effect.
So you shouldn’t technically do your cardio either before or after lifting weights. Ideally, you’d do your cardio on your rest days. If you want to bang out your cardio in the same session as your weight training, though, you’ve got a couple of options (study):
- Do your heavy lifting, then do some HIIT on a stationary bike. HIIT requires quite a lot of muscle strength, so it’s not going to interfere with the muscle-growth stimulus. If anything, it’s just going to give your legs some extra training volume.
- Train for strength first, then do your cardio. If your goal is to lift as heavy as possible in order to get bigger for your size—i.e. strength training—then it might make sense to do your lifting while you’re feeling fresh. Do your heavy squat sets first, then do your cardio afterwards.
- Do an easy cardio session first, then train for muscle growth. If your goal is to gain muscle size, it’s often better to do your cardio first, then gear into your hypertrophy workout afterwards. It’s okay if you’re a tiny bit tired while doing your hypertrophy training, and this will ensure that the final signal you’re sending your muscles is to grow bigger.
So assuming your goal is bulking up, I’d recommend doing your cardio on your rest days. But if that’s not feasible, then do an easy cardio session before your hypertrophy workout or an intense HIIT cardio session after your workout.
Should You Do Your Cardio Fasted?
The short answer is no. There are no fat-loss or performance benefits to fasted cardio. Moreover, delaying your first meal to squeeze in some cardio will only make it harder to reach your calorie goals.
The longer answer is the same, just more emphatic: absolutely not. We’re not trying to lose weight, we’re trying to get some extra cardiovascular fitness benefits while building muscle. To do that, we should be doing our cardio and weight training in a fully fed state, which will not only improve our training performance but also make it easier to recover from that training. And besides, intermittent fasting isn’t good for bulking anyway.
Just to add some nuance to that, though, if you’re doing some easy steady-state cardio before having breakfast, it’s not the end of the world. Not all skinny guys have trouble eating enough calories to gain weight. And a small decline in performance won’t cancel out the benefits of doing the cardio. But there’s still no benefit to it.
For your general health, your longterm goal should be to do at least 150 minutes of cardio and at least two strength-oriented workouts every week.
Since we’re naturally skinny guys, I think it makes more sense to invest a little more heavily into gaining muscle size and strength, at least until we accomplish our bulking goals. I’d personally recommend doing three bulking workouts every week. But that’s just my own opinion.
If we do three bulking workouts every week, and each lasts about an hour, then that counts for 90 minutes of cardio. That leaves 60 minutes of cardio to account for. We can get that cardio from brisk walks, playing sports, being physically active, or doing dedicated cardio workouts.
I get most of my additional cardio from walking, often while carrying heavy things: groceries, my son, a backpack, etc.
While you’re trying to bulk up, you probably don’t need to worry about cardio one way or the other. If you like doing cardio, feel free to keep doing it while bulking. You don’t need to worry about the interference effect. You’ll build muscle just fine.
But if you don’t like doing cardio, just save it for later. Your lifting workouts will likely provoke some beneficial cardiovascular adaptations anyway. Your general health will likely still improve and you should still be able to make fairly lean gains.
If you’re lifting and doing cardio, make sure that you’re not too intense about it. For example, going on long jogs, especially if you aren’t any good at running, can bang you up. It’s going to be hard to do your deadlifts if you’ve got shin splints. It’s going to be hard to squat if your knees are cranky.
If you’re new to cardio, better to choose the lower-impact forms, such as ellipticals, swimming, biking, or even just going on brisk walks. You’ll get the cardiovascular benefits but you’ll be saving most of your energy for your bulking routine, which is presumably your main goal right now.
The same goes for your bulking workouts. Those can bang you up, too, if you aren’t prudent about it. Low-bar squats might be hard on your hips, so choose better squat variations (such as goblet or front squats). Don’t lift to failure too often. Follow a professionally programmed bulking routine. Get plenty of good sleep.
Just generally keep your recovery in mind.
The most important thing is eating enough calories to gain weight. If cardio makes it harder to eat enough calories, save it for later. If you can’t eat in a calorie surplus, you won’t be able to bulk up. That’s the only way that cardio could destroy your gains.