Cardio gets a bad rap in the Paleo world. It’s dissed as inefficient, ineffective for muscle building, and just plain boring. Many people who discover Paleo are overjoyed to find a health philosophy that doesn’t require penitential hours on the treadmill or elliptical trainer.
That’s fine. If you hate cardio, don’t do it. Forget about it! Throw out the treadmill, burn your running shorts, and dedicate yourself to deadlifting three times your bodyweight. Or take up sprinting. Or go to Crossfit. Walk to work in the morning. Do whatever else you like. Nobody has to do cardio to be healthy.
But not everyone hates cardio. In fact, some people like it, and they don’t want to give up their long runs for a loaded barbell. Just like the natural strength athletes are miserable on the treadmill, natural cardio-lovers may be miserable in the weight room!
In an ideal world, nobody should have to do an exercise they hate - not the cardio lovers, not the power athletes, not the sprinters. Nobody. So if there’s a way that cardio can fit into a healthy Paleo lifestyle, wouldn’t it be great for the people who really want to do it?
In this article, we’ll look at three issues:
- Why does cardio have such a bad reputation, and does it deserve all the negativity?
- How does cardio compare to strength training for overall health? (to skip down to just that part, click here)
- How does cardio compare to strength training for weight loss? (to skip down to just that part, click here)
Philosophy vs. Activity: Or Why Cardio Isn’t as Bad as you Thought
One of the big reasons why cardio gets such a bad rap is that it’s so easy to overdo. In current exercise culture, there’s very much a “more is better” approach. If running a 5k is good, a 10k must be better! If a 10k is good, a marathon must make you immortal, right?
But wait just a minute. We need to distinguish between philosophies of training and specific activities.
Philosophies of training: the approach you take to your sport, whatever the particular sport is. For example: “More is better” vs. “work smarter, not harder.”
Specific activities: what motions your body is actually going through, regardless of your attitude. For example: Cardio vs. sprinting vs. weightlifting.
You can think about them in a 2x2 table, like this:
|“More is better”||“Work smarter, not harder”|
|Cardio||Result: “chronic cardio,” low energy, high stress response.||Result: cardiovascular fitness; better health.|
|Weightlifting/sprinting||Result: hormonal dysregulation, low energy, high stress response.||Result: Increased strength; better health.|
The “more is better” approach is dangerous no matter what specific activity you’re doing. Exercise is a stressor. The benefits of exercise aren’t from the exercise itself - they’re from the way your body adapts to the exercise and becomes stronger. To adapt, your body needs recovery time: just working out more and more will do absolutely nothing if it compromises recovery time.
Dr. Kurt Harris very correctly points this out here and here when he notes that regular marathon runners are at increased risk of heart disease. Very true: running multiple marathons every year definitely falls into the “inadequate recovery” danger zone. It’s a perfect illustration of why more is not better.
But regular marathons are not the only form of cardio around! Cardio does not have to be undertaken in the “more is better” mindset. We’re only used to associating them because the same people who push cardio also push the “more is better” mindset.
But what if we turned that around? What if we looked at cardio from the “train smarter, not harder” perspective, or even the “move for pleasure” perspective?
That might look like a run on Saturday morning when it’s a beautiful spring day and you just can’t stand to be inside any more - or maybe even a run in the middle of winter, on those days when you just want to wake up and grab the world by the horns. It would also mean skipping the run if you felt sore or exhausted, or cutting short after three miles instead of pushing yourself through all six.
This has absolutely nothing to do with the ultramarathoners who boast about pushing it so hard that they pee blood. It’s about a human movement - running - done in a way consistent with human biology.
Cardio vs. Strength Training: Overall Health
So considering that “cardio” does not have to mean “hours on the treadmill” or “running through repetitive stress injuries until your knees give out” or even “forcing yourself through the least mile when you really want to get off the bike and die,” it starts seeming a little more realistic that cardiovascular exercise might be part of a healthy Paleo exercise routine.
Cardio and Cavemen
At this point, it’s time to bring up the old argument that “cavemen didn’t do cardio.”
The theory goes like this: nobody in the Paleolithic “exercised” for the sake of burning calories. They had no survival reason to run marathons; their physical activity would have been primarily low and slow (walking from campsite to campsite) or short and intense (Look! A tiger! RUN!), without much in between. Therefore, our bodies are adapted to sprinting and walking, but not much in between.
But the fact is: we don’t know what cavemen did or didn’t do. We have no idea. Maybe they ran for fun – the Tarahumara certainly do, and running was part of their culture long before they’d ever heard of “burning calories.” Maybe cavemen also engaged in persistence hunting sometimes; we have plenty of records of human tribes who literally ran animals to exhaustion as a way of getting food. Maybe cavemen swam long distances, or did other “cardio-like” activities to build shelter or find food. We don’t know, and it’s pretty silly to make definitive pronouncements about “what cavemen did.”
But the bigger point is that Paleo is not about imitating cavemen. It’s about learning from our ancestral lifestyle to find things we can apply to the modern world. So whether or not cavemen ran 10ks isn’t really the question. The question is: is a moderate amount of cardio healthy for a human living in the 21st century?
And the answer is: yes.
Moving Past "What Cavemen Did:" Cardio and the 21st Century
First of all, cardio (like weightlifting) has metabolic benefits. It improves carbohydrate tolerance and reduces insulin resistance. This is a necessary prerequisite for weight loss.
- In this study, aerobic exercise in overweight teenagers dramatically improved insulin sensitivity even when it had no effect on weight.
- In this study, six months of consistent aerobic exercise improved insulin sensitivity in adults with impaired glucose tolerance.
There are more, but you get the idea: if you’re exercising to improve carbohydrate tolerance, cardio is a perfectly viable option.
Cardio also helps improve the other hormonal and metabolic challenges of overweight. For example, this review explains how exercise, including cardiovascular exercise, decreases inflammatory signaling in fat tissue.
It’s true that cardio doesn’t have all the benefits of resistance training. It’s not great for building muscle mass, and it isn’t as good for bone density. But cardio also has some benefits that strength training doesn’t have. For example, cardio builds endurance – and despite the naysaying of the “strength only” crowd, the ability to run a mile probably has more functional applications than the ability to deadlift 600 pounds. Think about it: when was the last time you had to pick up a car? Probably not very recently. But when was the last time you had to run for a bus? Dash through the airport to make a tight connection?
This review also gave aerobic exercise (namely cardio) a slight edge in improving blood pressure and cardiovascular health, while acknowledging that resistance training is also beneficial. So while marathon running may be dangerous for your heart, going for a jog every now and again just isn’t the same thing. It’s not even comparable. So it’s well past time to stop using ultramarathoners as “evidence” that cardio is dangerous. Unless you’re actually running marathons, studies on marathon runners are not relevant.
The upshot is that neither kind of exercise is definitively superior. Resistance training has some benefits; cardiovascular training has other benefits. At a moderate volume, with adequate rest and recovery time, there’s no reason to be afraid of either.
Cardio and Weight Loss
If you skipped down to this part of the article right away, consider going back up and reading the previous section as well (click here to do this): overall health is part of weight loss, and weight loss without health improvement is unlikely to stick!
With that said, how does cardio exercise compare to resistance training for weight loss specifically?
There are so many schools of thought on this. Everyone has their own favorite theory, but so many of those theories are really based on small studies, studies that have never been repeated, or studies done in populations that just aren't representative. Not everyone responds to exercise in the same way as untrained college-age men!
To help clarify, take a look at two of the biggies: which type burns more calories, and which type creates the greatest real-world weight loss in experiments where the weight loss itself (not just the calorie burn) is measured.
First, let’s talk about which type of exercise burns more calories. The interval training/weightlifting proponents and the cardio lovers both claim that their favorite exercise is the best. But in reality, they’re about the same.
First of all, the actual calorie burn is about the same for equivalent time spent on sprinting and jogging. 8 minutes of tabata sprints (20 seconds on, 10 seconds off) will burn approximately the same number of calories as 8 minutes of jogging, because even though you're working harder during the work period, you're resting ⅓ of the time.
The same goes for lifting heavy weights. The actual lifting burns more calories per minute, but as the weights go up, so do the rest periods, and the percentage of your “workout” that you spend in calorie-burning activities shrinks. So in the end, one hour of weight training burns even fewer calories than one hour of jogging.
But what about EPOC? EPOC, or Excess Post-Exercise Oxygen Consumption, is the number of calories you burn after the workout is done. It’s commonly repeated that high-intensity exercise burns more calories from EPOC, but this is irrelevant. The difference exists, but it’s tiny (you can read about this here). The post-exercise calorie burn for cardio is about 7%, while for sprinting it’s about 14%. That’s a 7% difference: it’s just not enough to have a huge effect one way or the other.
This doesn’t mean that sprinting or weightlifting are bad. They have other benefits. But for calorie-burning purposes, they have no magical metabolic advantage. Cardio is just as good – or probably even better, because you can do it for longer. If you want to get an extremely detailed look at exactly why this works, this series is a god place to start.
Real-World Weight Loss
Moving from counting calories to studies that actually measure the desired result (weight loss), there’s just not a lot to go on. There are a few studies – like this one, which compared a terrible cardio program to a terrible resistance training program. Strength training increased muscle mass; cardio reduced weight but also reduced muscle mass; the combination increased muscle mass while reducing fat mass just as well as cardio did. This study found pretty much the same thing.
This seems to suggest that the combination folks have it right. On the other hand, this review of the studies reported that there was insufficient data to really get a good comparison.
But the bigger picture is: exercise alone is not effective for weight loss. Regardless of which type of exercise burns more calories, exercising to “burn calories” is futile in the first place. Most of the exercise-only studies are comparing two absolutely tiny amounts of weight loss: either result would be very disappointing in the real world.
In study after study, exercise improves fitness, and helps prepare the body to lose fat through hormonal changes like increased insulin sensitivity. But exercise alone does not create much fat loss without an accompanying change in diet. In this post, for example, one researcher shares the result of an exercise-only intervention that he personally carried out: great routines, great adherence…and disappointing weight loss, because there was no dietary intervention.
Think about it this way: if weight loss is like a journey, exercise is like shoveling out your driveway before you leave. It’s necessary, but it’s not enough all on its own.
At this point, we know two things:
- Cardio and weightlifting both have metabolic and hormonal benefits.
- These metabolic and hormonal benefits – not “burning calories” – are the main reason why exercise helps with weight loss, in conjunction with diet.
This suggests that the best exercise for weight loss is whatever the individual enjoys and whatever they will keep doing. There may be a small advantage to a mixed routine – and this is something many people will naturally gravitate toward anyway, just out of curiosity and the desire to explore new ways of moving. But so far, the benefits of intervals or weightlifting over cardio for weight loss are mostly hype. The most important factor in weight loss is diet, not exercise - and as long as you get some kind of exercise, it doesn't seem to be hugely significant what particular kind it is.
Any exercise is bad for you if you overdo it. You can beat yourself into the ground with weight training just as well as with cardio. To borrow a famous phrase, you could do chronic Crossfit just as easily as chronic cardio – and it would be just as dangerous.
But it’s time to separate cardio from the “more is better” philosophy. More is not better, but there’s a way to enjoy cardiovascular exercise without compromising your recovery or health!
Again, this doesn’t mean that cardio is healthy for everyone, or that it’s required for physical fitness. Every person has a different body type, and different body types are naturally better suited to different exercises. Some people do not do well with cardio, and that's perfectly fine: just don't do it.
The point of this article isn’t to push cardio on people whose bodies don’t respond to it; it’s to point out that some of us are built more for distance work, and that’s OK, too. It’s fine to do cardio if you like it. Cardio does not make you fat. Cardio does not make you sick. It certainly will not give you a heart attack. Overtraining can make you fat and sick, but cardio does not have to be taken to extremes. If running (or swimming, or biking, or rock climbing, or jazzercise…) is your favorite way to get up and move, do it, and enjoy it!