The Exhaustive Debate: Cardio or Strength Training?
Why lifting weights is not better for you than running, and the other way around
People know they need to exercise more. Massive public health campaigns are aimed at getting them off the couch and onto a bicycle. Tweets from fitness experts bandy about words like “myofibril,” “isometric,” and “sweat.” Nearby gyms will sell people the ability to do a pullup in six months if they’d only sign away 10% of their income. People know they need to exercise more. What they don’t know is how.
There’s a lot of debate about whether cardio (aerobic) exercise beats resistance (strength) training. Cardio usually takes the form of running, cycling, or swimming. Resistance training often involves weightlifting.
A common refrain is that cardio is the best thing for losing weight or improving heart health, and resistance is the best thing for building muscle (though without any cardiovascular benefits). But is that really the case?
Sports science is complicated
The problem is that in sports science, solid advice based on big scientific studies is quite rare. It makes sense when you think about it: Unlike clinical medicine, where a company can earn hundreds of billions of dollars down the road after developing a single drug, there’s not as much motivation (or money) behind finding the perfect workout. What’s more, as a society, we are generally more interested in knowing which medications prevent heart attacks than in whether crunches or situps are more effective.
It’s also really difficult to run studies on physical training and exercise. If you recruit people who are already fit, your findings will be less impressive and the conclusions less generalizable. Go the other way and recruit untrained people, and you might end up with no result because the subjects didn’t understand how to do the exercises well enough.
Moreover, scientific studies are expensive, and sports science studies are no different. Getting people to follow an exercise plan requires quite a bit of money, especially when you’re also testing complex physiological parameters. This means that many studies in the field have too few participants to make a solid conclusion.
When it comes to comparing cardio and resistance training, the evidence doesn’t show a benefit either way. One large systematic review — a type of meta-study that collates evidence from an entire field of research — focused on mentions of visceral fat in studies comparing the two forms of exercise. This is the fat that builds up in your torso and is thought to be the primary driver of obesity-related disease, which makes it an important indicator for health. The systematic review combined the results from 35 studies looking at more than 2,000 people across a wide range of exercise regimens. In terms of visceral fat, the review found that cardio provided benefits, but when compared to resistance training, the data was inconclusive.
Like most studies in the field, those comparing cardio and resistance training are few and far between. Another review, this one from 2018, looked at a range of health factors. Researchers found more than a dozen studies showing that cardio improved health, but only a handful compared cardio and resistance, and those lacked enough evidence to draw any conclusions at all.
It all depends on how much you’re already doing
One important factor to consider in a comparison of cardio and resistance is the idea of marginal benefit — essentially, the amount of good you will get from something above and beyond the good you’re already getting. For example, if you go to the gym once a month and add an extra session to make it twice a month, you’ll probably notice some results. If you go to the gym five times a week and add one session a month on top of that, the marginal benefit of the extra session will be tiny.
In other words, the question of whether to run on a treadmill or lift weights might be a moot point when compared to the benefit of doing any exercise at all.
The point is that if you go from one session per year to one a week, it probably doesn’t matter what you’re doing — squats or lunges, deadlifts or rows — you’ll see improvements regardless.
Take one study from 2017. Researchers randomly assigned 160 obese participants to do resistance, cardio, both, or nothing for six months and tested them on a range of factors at the end. The exercise consisted of three 60-minute sessions per week. The researchers found that people who did some cardio — either as their only exercise or as a combination — saw a bit more improvement in heart health than people who did only resistance. They also saw that people who did any resistance training improved more in terms of lean muscle mass and bone density. But even then, the improvements were small; for example, the change in lean muscle mass between the cardio and resistance groups differed by less than 1%.
The point is that if you go from one session per year to one a week, it probably doesn’t matter what you’re doing — squats or lunges, deadlifts or rows — you’ll see improvements regardless. And whether you choose cardio or resistance, in the end, there isn’t much difference between the two.
If the science indicates a basic equivalence between the two forms of exercise, it also points to the benefits of lifting weights to build and preserve muscle. If you want to get swole, based on evidence, the best thing to do is to pump iron.
Naturally, it’s a bit more complicated than that. While cardio and resistance were once completely separate ideas, more and more programs actually combine the two — think CrossFit or Body Pump — boosting your heart rate for an hour while also lifting. And while the evidence for this type of combination training may not yet be robust, studies like the previously mentioned randomized trial have found that such regimens may offer all the benefits with none of the downsides.
Overall, it seems that exercise is exercise, whether it’s lifting weights or spinning. There might be minor benefits of one over the other, but realistically, the difference is small.
Also, there’s no reason you can’t do both: Warm up with cardio and then lift weights to get the best of both worlds.