When you see the biggest guy in the gym pull up to the weight room, you might assume he’ll be reaching for the heaviest weights. You’ve gotta pump massive iron to build massive muscles, right? Well, not really.
“There's a lot of lore around this routine or that routine, and a lot of it comes from former Soviet bloc country training regimens where most people were taking steroids,” says Stuart Phillips, PhD, a kinesiology professor and research director at McMaster University. Some of it also comes from a misunderstood study from 1946: While rehabilitating soldiers from World War II, army physician Thomas DeLorme argued that heavy resistance training was better at building muscle than, say, repetitive activities like walking or biking, and for decades, many took that to mean only heavy weights were helpful, says Dr. Phillips.
Yet the more scientists look into it, the more they’re finding that heavy lifting isn’t a prerequisite for growing muscle, or as the experts call it, “hypertrophy.” Recently, Dr. Phillips led a network meta-analysis published in the British Journal of Sports Medicine that looked at 192 randomized, controlled studies with a total sample size of more than 5,000 people to find the “optimal prescription for hypertrophy.” What his team discovered shocked many. “You can lift lighter weights, and as long as you lift them with a high degree of effort, they're as good as heavier weights in making you bigger,” he says. Even just using your own body weight, like with push-ups or lunges, works. The key is simply to get pretty close to what personal trainers call “failure,” or the point where you feel like you can’t keep going any longer. That could take up to 25 to 30 reps, and you’ll still build muscle, says Dr. Phillips.
To understand the physiology at play, it helps to know the difference between our two types of muscle fibers: fast twitch, or type II, produces force but fatigues quickly (think sprinting), while slow twitch, or type I, gives us endurance but aren’t super powerful (think marathon running). When you want to get bigger, it’s the fast twitch you mostly want to target since those have between 30 to 50 percent more growth potential than their slow counterparts, says Bradley Schoenfeld, PhD, graduate director of the Human Performance and Fitness program at Lehman College, who wrote the book Science and Development of Muscle Hypertrophy.
While it used to be thought that only heavy loads—weights you can only lift about three to five times—could activate the fast-twitch fibers, we now know that’s not the case, Dr. Schoenfeld says. “Provided that you train with a lot of effort where the last reps are difficult to complete, you will recruit the majority of the fast-twitch muscle fibers,” he says. “Muscle growth tends to be the same.”
That said, if your goals are more about strength than size, you’ll want to keep reaching for the largest dumbbells. Our bodies get better at what we practice, so if you want to be strong enough to lift heavy things, you have to practice lifting heavy things, Dr. Phillips says.
But if getting big is primarily what you’re after, rather than worrying about how much weight you’re hauling up and down, the key is to focus on doing multiple sets. “There's a certain amount of work you need to do that signals to your muscle to induce growth, to get bigger,” Dr. Phillips says. Exactly how much volume you need to put in, however, is an ongoing debate. The BJSM analysis found you need to complete at least two sets to near fatigue to grow muscle and suggested that training twice a week is more effective than just once. But doing more and more won’t make you bigger and bigger because, at a certain point, the benefits plateau.
“My analogy is always, imagine if you dip a cloth in water and you're squeezing the cloth. So you twist it once, that's one day a week. You twist it twice and you get a little bit more water. You twist it a third time, and now you're getting some water out, but it's much less than you got out on the first and second twist,” says Dr. Phillips.
What the science is unequivocal about is that in order to make gains, you need to be consistent—which is something that we know can be easy to make and easier to break. To get yourself to hit the gym regularly, sport and performance psychologist Marla Zucker, PhD, CMPC suggests strategies like reminding yourself of the reasons why you work out, setting some short-term goals (ones that you can actually accomplish), and working out with a coach or accountability buddy to give you some camaraderie and help you enjoy the process.
Because…you have to like your workout enough to do it over and over again. Don’t make yourself suffer through it. “If you hate an exercise, there's no exercise from a muscle growth standpoint that you have to do,” says Dr. Schoenfeld. “Different exercises can accomplish similar things, so pick exercises that you like.” And do them with any weights you want as long as they bring on that burn—even if that means that you’re doing more reps than the guy grunting next to you.
Originally Appeared on GQ