As a personal fitness trainer, I get asked this question a lot. Someone will read a magazine article touting the fat burning zone in cardio and will freak out every time I hand them a dumbbell, thinking that I have secret intentions to bulk them up. Here’s the truth…

Your Body Doesn’t Differentiate Between Cardio and Strength Training

Your body doesn’t have an “absolute cardio mode” or an “absolute strength mode.” The difference was made by humans trying to understand the body.

There is a difference in percentages, but there is not a situation where your body says “Oh, I’m doing cardio now.” The body simply reacts to the various stresses put on it.

Sometimes the stress involves a large amount of weight and sometimes it is the fact that a motion is repeated over and over.

How the Body Was Designed

I don’t have any inside information on this – whether it was evolution or creation or whatnot – but your body doesn’t have a “cardio” mode or a “strength” mode. It does, however, have a “SURVIVE” mode. It will do whatever it needs to do in the moment to survive. Whether survival means running fast, climbing a wall or lifting a heavy weight off yourself, your body will perform at its best to keep you alive.

THEN after you survive that feat, your body will allocate resources based on what it needed to do to survive. If you stressed your cardiovascular system, it would put some more resources there to reinforce that line. If you stressed the strength of your muscles, it would devote resources to rebuilding those muscles to be stronger.

First stimulus, then response. You, as a being, are not Pavlov’s dog, but your muscles react to a given stimulus in a very predictable way.

The distinction between these two was the brainchild of man trying to understand his body (and we still have a LONG, LONG way to go before we understand our bodies). This was not the discovery of an actual fact. It is one of those things I have to unteach people.

An Example of Cardiovascular vs Strength Training

Let’s say you take an untrained person and put him on a running program. His muscles are going to be sore from the exercise. He is going to build strength and endurance. You are training his strength and his cardiovascular system at the same time.

Let’s also say you take a person and have him do heavy weights on the bench press, leg press, bicep curls and triceps extension machines – but you don’t give him the customary five minutes to bullshit with his buddies in between sets. His heart will be racing and he will be sweating as if he has been running.

So you tell me the difference.

Blur Your Approach – It’s Not Cardio vs Strength Anymore

The line is definitely blurred so I suggest that you blur your approach to the whole thing as well. Gone are the days of 80s body builders and their lingo. I personally can’t stand the 80s, but I will admit that it was a necessary phase to go through in the exercise world. (The clashing colors thing is a topic for another time.)

Some really good stuff came out of that era, but some bad stuff does still kick around here and there. I have to teach people that fat won’t kill them and that it is okay to mix cardio and weight training.

The old style was clearly defined between cardio people and bodybuilders. There wasn’t a “I do a little bit of both” section in the gym. Or even an “I dominate at both” section. You were one or the other, buddy. If you were out of breath from a sprint and you touched a dumbbell, you got some weird looks. The cardio guys were like “that muscle is weighing him down” and the muscle freaks were like “that cardio is eating up his muscle.”

The truth is that you are just stressing your body in a different way.

How People Caught On To Cross Training

It literally took years and several very formal studies, well written and peer reviewed, to teach everyone that strength training actually benefited runners. It was accepted as much as a dead cat at a wedding. Sure, some coaches were bright enough to see this years before because they had their guinea pigs right in front of them and had their own results.

But the “general populous” or whatever you want to call it, didn’t catch on. To be more specific: it wasn’t seen in every fitness facility right away. It took years and years before it caught on in the mainstream. The pioneers of this movement got tons of crap. You just need to look at the evolution of gym designs to see the difference here. There has been a trend toward massive open spaces and free weights.

Many of the strength and conditioning coaches – the real specialists – trained their athletes in ways that produced the best results. I don’t condemn any of them. I have so much respect for that environment because it is a perfect way for youth to spend their free time, we are pushing the limits of human performance and it is just so much fun and so rewarding.

I do, however, condemn trainers who didn’t try it out for themselves or try it on their clients. A personal fitness trainer in a gym is very much driven by money, where a coach in a university is driven by performance.

My Confession

I went through a period where I knew very little and I preached the exact things I am preaching against right now.

I trained a high-school kid named Benny who was already pretty stout, but wanted to be a walking muscle. I would have him walk on the treadmill for 5 minutes to warm up. Any more than that and I was scared I was going to start eating up his muscle. There was no point in the workouts where he was out of breath. We gave ample time between sets (and accordingly spent the time talking about girls and trucks). He got bigger but he did not train his heart much.

“Strict” bodybuilding rules were followed and the end result was a dude who was likely to twist an ankle if he went to play Ultimate Frisbee. The extra risk with these types is that they think they are fit, but they’re not. They’re not “fit” in all ways. “Fit” is a funny word that originally meant “able to reproduce.”

Just because you can lift heavy doesn’t mean that you can sprint fast. Just because you lift heavy doesn’t mean you can jump high or even have the coordination to land on your feet. Out of all types of people I have trained “heavy lifters” are most commonly injured outside of the gym doing things they thought they should be able to do.


Nature didn’t define cardio and strength training differently. The two are always at work and the difference is only in percentages. So, when you are building your own exercise program. Figure out what percent “strong” you want to be and what percent “cardiovascular” you want to be.

There are benefits to both. Strength training prevents and even handles osteoporosis and osteopenia. Strength training corrects posture, stabilizes weak joints and makes you look good naked.

Cardio training improves your heart’s performance. It lowers the amount that it has to work at rest. If there is one type of training that I would have people do for the rest of their lives, it is cardio. Based on the studies that I have read, it produces the most longevity. I mean literally, the biggest increase in numbers on your life. When you do “cardio,” you are working all sorts of muscles out anyway and keeping them in shape (so there’s a bit of strength training in cardio).

So figure out what percentage of the two you want to mix up and build your program on that. Or if you want to go hardcore on one and not the other, that is fine too.

At the end of the day, I’m just happy to see people working out.

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