Muscle Professor Academy Q&A | The Science Behind Cardio For Fat Loss

Muscle Professor Academy Q&A | Are HMB Supplements The Secret To Muscle Growth?


Jacob M. Wilson, Ph.D., CSCS*D

Dr. Wilson: The only way I can really get lean is by adding in a lot of cardio. 

The main problem is that I always end out losing loads of muscle.  Any advice?”

One of the undeniable hallmarks of a great physique is a nice clear foundation of symmetrical muscle. The other is razor-sharp conditioning. Look at pretty much everybody’s program, and you’ll see how they approach these two goals:

1) Resistance training to build muscle

2) Cardio to burn fat….Simple enough, right?

The science backs up the effectiveness of these two modalities. It’s where they mix, in “concurrent training,” that things get complicated. For instance, a study published in the Journal of Applied Physiology in 1998 found that 10 weeks of resistance training plus cardio resulted in greater fat loss than lifting weights alone. Unfortunately, in that same study, strength gains were cut in half when cardio was added to weightlifting.1 Other studies have similarly found that muscle growth is severely decreased when cardio is integrated into a program.2,3


Does cardio affect muscle gains?

There are a number of explanations as to why cardio blunts gains:

? One is that cardio adds extra volume to your training, making it difficult to recover from normal lifting.4

? Other researchers maintain that the physiological adaptations that follow cardio training are the complete opposite of those which occur with lifting weights, and that cardiovascular gains are thus capable of cancelling out gains from weight training.5

Both of these scenarios imply that those trying to gain muscle are paddling upstream when they begin trying to cut fat. So is it really impossible to maximise the positive effects of cardio, while eliminating the negative?

My colleagues at Applied Science and Performance Institute and I have been studying this question in recent years, and we have some good news for you: It is possible. It all depends on what type of cardio you choose, and how much of it you perform.

Pedal Away From The Treadmill

One of our recent studies investigated the effects that different types of cardio, their intensity, and the separation of cardio from lifting had on muscle size.6 The goal was to determine exactly which components of cardio hinder resistance training results.

STUDY | Cycling vs Running 

For instance, when we compared cycling to running, we found that running caused far greater declines in muscle growth than cycling. This has been supported in another study in another lab, which found that slow uphill walking produced greater declines in strength than cycling.7

There are a couple of explanations for why this is the case.

1) The first is that the range of motion you use when jogging or incline walking is so dissimilar from lifting weights—squatting, for instance—that it impairs strength gains in those lifts. Unlike running, however, cycling has a large range of motion that is similar to squatting and leg pressing.

2) Another theory is that cycling is mainly a shorting/concentric movement and causes little muscle damage, whereas running causes a lot of muscle damage from its lengthening / eccentric portions.8 This would make it easier to recover from cycling than from running.

The Importance of Intensity

Intensity and duration have an even greater effect than the type of cardio you perform. Our study concluded that long-term fat loss is actually lowest with moderate intensity, long-duration cardio.

The greatest fat loss actually occurred with the shortest duration and highest-intensity activities, like sprinting. We also saw that the longer you perform cardio per day, the greater the losses are in muscle mass. However, we found very small decreases in muscle and strength when cardio was kept to less than 20 minutes per day.

“But what about the ‘fat-burning zone?'” you shout from the treadmill! By this, you refer to a study conducted in the early 1990s by Dr. Romijn, who concluded that we use the most fat during exercise when performing moderate intensity (65 percent heart rate max), long-duration (45-60 minutes) cardio.9 This study’s conclusions are reflected in the “fat-burning” programs on nearly every cardio machine at the gym. However, a major problem with the study is that what happens during exercise does not always reflect what will occur long term. I want to hammer this point home.

Sprinting for muscle gains

Sprint Training Drills For Lean Gains & Fat Loss

My lab recently conducted another experiment where we compared low-intensity, long-duration cardio of 60 minutes with 4-10 sets of 10-30-second all-out sprints. As expected, we found that long duration cardio decreased muscle size.

But get this: Sprinting actually increased size.10 This suggests that sprinting can actually be anabolic and get you shredded at the same time!


The bottom line is that a major way cardio works to enhance fat loss is by increasing calorie expenditure >> thereby causing a calorie deficit.

When you are in a deficit you are in danger of losing muscle.  Researchers have found many ways to counter muscle loss using nutrition and supplementation interventions.

While an in depth discussion of these is beyond the scope of this article we do know that higher amounts of:

Whey protein powder – lean muscle growth & recovery

Branched Chain Amino Acids (BCAAs) – muscle recovery

HMB supplements – Amino acids to contribute to muscle growth

Phosphatidyl serine – Naturally occurring supplement

These can blunt the negative effects high volumes of training can have on muscle recovery.  Thus, these supplements can serve as a strong tool in your battle to get lean, but keep the metabolically active muscle!

After strategically implementing these anti-catabolic nutrition interventions into your regimen, it’s time to put it all together!

Put It All Together |

High-intensity sprinting leads to greater fat loss than low-intensity, while also maintaining and possibly increasing muscle mass. That being said, sprinting isn’t easy to get started with, so it’s necessary to approach it methodically.

Sprint Training Drills For Lean Gains & Fat Loss

Individuals seeking fat loss should try performing 10-30 second all-out sprints for between 4 and 10 reps. When I say “all-out,” I mean you should feel like you have nothing left at the end of the sprint. However, I recommend beginning at the lower range and working your way up.

Once you establish your conditioning, which will likely take at least a month, you should begin to periodise your sprinting protocols. For example, if you do three sprinting sessions per week, I recommend one to be shorter duration and really high intensity, such as six 10-second hill sprints.

One could be moderate duration, such as six 15-second sprints on flat ground. And finally, one should be longer, such as four 30-second all-out cycling sprints. I’m also a fan of all out brutal activities like car pushes and prowler or car pushes.

TRAINING TIP | Separate your cardio and leg days

Try to separate your cardio from leg days by at least a day. Our lab and others have found that the effects of cardio are specific to the muscle worked. So if you do leg-intensive cardio today, it will directly affect muscle growth in your legs.

What research shows clearly is that cardio ideally should be separated from legs by at least 24 hours. Otherwise you risk impairing your gains.11

Take Home Message

That may sound like a lot of guidelines, but just think about all the time you’re saving by not spending hour after hour on the treadmill.

It’s definitely worth a little bit of extra planning!

Our articles should be used for informational and educational purposes only and are not intended to be taken as medical advice. If you’re concerned, consult a health professional before taking dietary supplements or introducing any major changes to your diet.



Writer and expert

Payday SALE | Up to 70% off | Use code: SALE Shop Now