Cardio and Muscle Mass Gains

Among the numerous never-ending debates in the field is the question of whether or not cardio/aerobic type activity should be performed when the explicit goal is maximum gains in muscle mass. And as is usually the case, there are a variety of extreme standpoints in this debate.At one extreme is the idea that trainees should perform an hour of low intensity cardio daily during their mass gaining phase. This is usually suggested as a way of staying lean during the period of overfeeding needed to maximize muscle gain. At the other extreme is the idea that any activity outside of lifting weights, and especially cardio, will do nothing but harm gains in muscle mass (and strength).

As usual, I think that the truth lies somewhere in the middle and I’d like to look at some of the various pros and cons of keeping some form of cardio in the overall program when the explicit goal is muscle mass gains. As usual, whether cardio is good, bad or neutral depends on the situation along with how it’s performed.

For context, the main type of cardio activity I’ll be focusing on in this article is low to moderate intensity steady state cardio which is usually where the big arguments erupt. For the most part, unless dealing with an athlete who must be performing interval training for their sport, I don’t recommend interval training when the goals are maximal muscle mass gains.

Yes, you can always find someone who makes it work (and there have been various theories thrown around how sprinting might enhance muscle gain which never seem to have really panned out) but for the most part I don’t think high intensity cardio training of any sort (interval or otherwise) is optimal when the goal is maximal muscle gain. So I’ll be focusing on low- to moderate-intensity steady state type cardio here.

Benefits of Cardio During Mass Gaining Phases

Among the pros of maintaining some amount of cardio during a mass gaining phase, I’d probably include the following:

1. Improved recovery
2. Appetite
3. Maintaining some conditioning and work capacity
4. Improved Calorie Partitioning
5. Keeps the fat burning pathways active

Let’s look at each.

Improved Recovery

Done at low to moderate intensities (I’ll come back to specifics at the end of the article) cardio can act as a form of active recovery. By pumping blood through worked muscles, recovery is often hastened (and for many, active recovery actually helps more than simple passive recovery: doing nothing).

I’d note that most forms of cardio tend to be lower body dominant so most of this effect will be for the lower body. Trainees who want to achieve a similar effect for the upper body would need to perform rowing or use the EFX or a machine that also involves the upper body to some degree.

Finally, it’s worth noting that, by sipping on a dilute carb/protein drink (perhaps 30 grams carbs and half as much protein per hour), the increased blood flow to the working muscles will enhance nutrient delivery; this should also help with overall muscular recovery.


The impact of exercise on appetite can be exceedingly variable. For some people, activity, and this is especially true of high-intensity activity, can blunt appetite; for others it can stimulate it. In the context of mass gaining, trainees who have trouble consuming sufficient calories often find that including moderate amounts of cardio can be beneficial in terms of improving appetite.

Maintaining Conditioning/Work Capacity

Depending on the specifics of the training, it’s not uncommon for lifters and trainees to lose a lot of their metabolic conditioning when they move into pure mass gain phases (where all they are doing is weight training). Lower repetition/long rest interval types of training tends to have the greatest impact and individuals lose vast amounts of conditioning and work capacity during this type of training.

For athletes this is clearly detrimental since it means they have to start building things back up from scratch. Even for non-athlete lifters (e.g. bodybuilders), losing work capacity can hurt overall recovery both during a workout and in-between workouts.

The good thing is that it takes far less training to maintain some conditioning than it does to develop it and keeping at least some amount of cardio in the total training program goes a long way towards this goal.

Improved Calorie Partitioning

As an additional potential benefit, aerobic activity could potentially improve results during a mass gaining phase in another way and that has to do with overall calorie partitioning. As I discuss in Calorie Partitioning Part 1 and Calorie Partitioning Part 2, partitioning has to do with where calories ‘go’ or ‘come from’ when you over- or under-eat respectively.

Probably the most potent partitioning tool we have is training. Regular activity increases nutrient uptake into skeletal muscle; practically that means less excess calories to get stored elsewhere (e.g. fat cells). While it’s debatable how much of an effect low- to moderate intensity cardio will have in this impact, it certainly won’t hurt done in reasonable amounts. And it may help in the long-term.

Staying Lean/Keeping Fat Burning Pathways Active

Finally, there is the issue of keeping fat burning pathways active and/or staying lean while mass gaining. Frankly, I’m not hugely convinced that doing cardio does a ton to keep folks lean; especially given that it’s relatively easy to eat more calories and overpower any slight caloric burn from the type of cardio that is usually advocated. Frankly, I suspect that it would be easier to just keep the caloric surplus under greater control (or time that surplus around training better).

However, there is another related reason to keep it in and that has to do with the fact that eventually folks who are gaining muscle mass will want to lean out. As I discussed in General Philosophies of Muscle Mass Gains, most will get the fastest rate of muscle growth while allowing some fat gain to occur; this necessitates eventually dieting off the extra fat.

Now, tangentially (and this is a topic I can’t discuss fully here), I think that one of the reasons that cardio has gotten a bad rap in terms of muscle loss on a diet is that people jump from doing basically zero cardio to fairly large amounts often overnight; this is often accompanied by a massive drop in calories and I suspect that it is this combination that tends to cause muscle loss.

This is a problem as during the overfeeding that is needed to generate maximum gains in muscle mass, the body often loses some of its ability to use fat as a fuel and this can take a couple of weeks to get fully ramped back up when calories are restricted (I suspect this explains some of the odd delay that seems to occur in true fat loss when people start dieting again).

And this seems to be even more pronounced if folks have been doing zero cardio while they are gaining muscle mass. By keeping in some amount of cardio during the mass gaining phase, at least some ability to use fat effectively for fuel is maintained. When the dieting phase eventually starts, the body will be a in better place to use fat for fuel.

Drawbacks of Cardio During Mass Gaining Phases

Having looked at the pros of keeping at least some cardio in during mass gaining phases, I now want to look at the two major cons, or at least the two that are usually brought up:

1. Burns up calories that could go towards muscle growth
2. Might cut into recovery/Over-training

Burning up Calories that could go to Muscle Growth

This tends to be one of the major concerns of the ‘no cardio while gaining mass’ group, that valuable calories that might go towards muscle growth will be burned off by cardio. And certainly, taken to the extreme where excessive cardio is being done, there is much truth to this.

As I mentioned above, the calorie burn of reasonable amounts of low to moderate intensity aerobic activity isn’t generally very high unless someone is exceedingly well trained (and can burn tremendous numbers of calories even at low intensities). The few hundred calories burned during activity is pretty easy to replace on a day to day basis and I’m not sure this is a huge concern in terms of preventing calories and protein from getting to the muscle to support growth.

One exception to this are the perpetually skinny (e.g. the classic ‘hardgainer’ or ectomorphic type). These are the folks who have a hard enough time putting on weight in the first place, for a wide variety of reasons (that I’ve discussed elsewhere on the site). Since they rarely have to worry about getting lean in the first place, they probably should avoid much if any cardio so that all of their energies and food intake go towards training and gaining muscle mass.

Of course, the exception to this exception relates to the appetite issue I mentioned above. The classic ectomorphic/hardgainer type often has trouble eating sufficient calories (one of the reasons they tend to stay so lean/skinny is that their appetite tends to shut off pretty readily when they overfeed). In that situation, if performing some cardio on off days helps them to eat more, then it might still be worth including.

Cutting into Recovery/Over-training

The final two issues I want to look at are extremely related so I’ll look at them together. The basic concern is that trying to combine both heavy weight training and cardio/endurance type training will impair results in the weight room. And there is certainly some truth to that idea.

A great amount of early research (and practical experience) suggested that the combination of cardiovascular and strength training tended to cause an interference in terms of results. Interestingly (and this is beyond the scope of this article), while cardiovascular training tended to impair strength performance, the opposite often wasn’t seen; heavy strength training didn’t seem to impair the adaptations to endurance training.

Now one factor to keep in mind is that most of the studies looking at this topic were using some fairly high intensity types of cardio; they were often examining the types of training that might be seen with American football or sports of that nature. Meaning that they don’t automatically have a ton of relevance to what’s being discussed in this article. The intensity is a key factor, for reasons that are beyond the scope of this article. When intensity is kept down and the volume and frequency is more moderate, the potential negative impact of cardiovascular training on adaptations in the weight room is massively reduced.

In that vein, I would still note that excessive amounts of cardio can still cut into recovery, both systemically (whole-body) and locally (specific muscle groups). The legs are what typically what can take a beating since most cardio modes are lower body dominant. Excessive amounts of even low intensity cardio can cut into the overall recovery of the legs and rotating machines to alter the stress on the musculature may be a worthwhile consideration.

So Cardio while Focusing on Mass Gains…Yes or No?

In my opinion, with the potential exception of the extremely skinny/hardgainer type (who may still benefit from appetite stimulation), there is more benefit to be had from reasonable amounts of cardio than there are negatives.

I simply feel that most of the problems with cardio training start to come into play when either the intensity or volume get excessive. As long as the amounts are kept moderate and the intensity is kept under control I think most of the concerns are mostly a non-issue.

So what defines moderate, reasonable, etc.?

At a bare minimum, 20-30 minutes of cardio performed three times per week will maintain some basic cardiovascular fitness, burn off a few calories, act as active recovery, and help to keep the fat burning pathways active so that the shift to dieting is a little bit easier; all of the good things that I mentioned. And it should do that without having any really major impact on progress in the weight room.

A higher frequency can be used but I wouldn’t see much point to more than five per week unless the intensity is kept very low (e.g. you can do brisk walking daily if desired). Going longer than the bare minimum of 20-30 minutes will burn a few more calories but there are limits to time availability (and people start to get bored) and I might set a reasonable limit of 40 minutes of moderate intensity cardio at the maximum; if the intensity is kept way down (again, think brisk walking), an hour is acceptable.

In terms of intensity, I think keeping things in the low to moderate range is going to be best. More specifically, a maximum intensity of 70% of maximum heart rate (140 beats per minute for someone with a maximum of 200 beats) or even lower should achieve some benefits without cutting into recovery or growth.

As I referred to in the first part of this article, it’s damn near a bodybuilding tradition to walk on the treadmill for an hour every morning and, while I think that amount is overkill for most, the intensity is definitely going to be low with that type of activity. That bodybuilders have done this successfully for so many years would seem to be an important lesson, especially for those folks who think that the only type of metabolic work worth a damn is high intensity stuff.

A final issue to examine is that of timing and when to perform the cardio. In an ideal universe, any cardio would probably be done completely separately from weight training. Cardio in the morning (fasted or not) and weights evening would probably be ideal but can’t always be realistically scheduled when people work full-time.

A very common approach is to perform some type of cardio on off-days from the weight room and this is certainly workable if scheduling will allow it. Of course, not everyone can make it to the gym daily and the weather or what have you may preclude doing it outdoors or at home. As well, for a short 20-30 minute session, making the trip to the gym (driving time may take longer than that) may not be realistic.

In practical terms, that means performing cardio in conjunction with the weight workout; this raises the question of whether or not it should be done before or after the workout.

As long as the intensity is kept low, doing a short cardio workout before weights shouldn’t hurt intensity in the gym (just think of it as a prolonged general warm up). Doing it afterwards has less potential to impact on the weight room session itself but, for those compulsive about post-workout nutrition, does delay eating. A reasonable compromise would be to drink your post-workout drink while doing your cardio after the workout.

I would note that, after heavy leg training, most probably won’t want to do much in the way of cardio. Keeping the session to the bare minimums (e.g. 20 minutes of pretty low intensity work) is probably best. Cardio done after upper body workouts can be a bit longer and/or more intensive if desired (within the guidelines I gave above).

Summing Up

So summing up, under most circumstances, I think keeping a reasonable amount of moderate intensity cardio in the training program, even when the goal is explicitly mass gaining can be beneficial for most trainees (the major exception being the extreme hardgainer types).

Potential pros include improved recovery, improved work capacity, better calorie partitioning, improved appetite (sometimes), perhaps staying leaner and an easier time shifting back into dieting when the mass gaining phase is over. The cons, including hampered recovery and systematic overtraining only really become an issue when too much volume or too high of an intensity is performed.

A minimum of three sessions per week (up to perhaps a maximum of 5) of reasonable duration (20-30 minutes minimum up to perhaps 40 minutes maximum) at a low to moderate intensity (70% of maximum heart rate or less) should achieve the benefits I talked about above without causing any of the problems that I also discussed.

* This article is EXCLUSIVE to, reproduction in any form without prior consent is strictly PROHIBITED.

If you would like further reading by Lyle McDonald please check out all of his ebooks on diet and nutrition at:

Body Recomposition