According to a new study of 42 healthy adult men and women, the answer seems to be about an hour a week. During the two-month study, participants gained significant muscle mass and strength from just two 30-minute sessions of uncomplicated resistance exercises each week.
The findings “highlight how powerful even a small amount of loading can be,” said Stuart Phillips, an exercise scientist at McMaster University in Canada who studies resistance training but was not involved in this research.
In each session, the volunteers completed nine common upper- and lower-body gym exercises, repeating each move eight to 10 times, until their muscles felt fatigued but not necessarily exhausted.
The routine was meant to be quick because so many people blame tight schedules for not lifting, said Brad Schoenfeld, a professor of exercise science at Lehman College in the Bronx and the study’s senior author. “We were interested in finding the minimum effective dose” of resistance training for most people, he continued.
In other words, they wanted to see, “how low can you go?” with lifting workouts, Phillips said. The results show “just how small of an investment we need to make to reap some, in my estimation, substantial rewards.”
Why most people don’t weight train
Almost all of us, if we’re capable of exercising, should be doing some type of regular “muscle-strengthening activities” for our health and longevity, according to recommendations from the Centers for Disease Control and Prevention. Strong, healthy muscles help protect us against diabetes, arthritis and a range of other diseases, as well as frailty and premature death.
But few of us lift. The CDC estimates, in fact, that barely 20 percent of American adults strength train even a few times a week.
“The main reason people give is time,” Schoenfeld said. Many worry, too, that weight training requires complex equipment and arcane expertise about loads, reps and other lifting matters.
So, for the study, published in April in Medicine & Science in Sports & Exercise, Schoenfeld and his collaborators put together a speedy, simple, full-body, gym-based workout, with exercises focused on the shoulders, arms, legs, back and core.
Then they rounded up a group of healthy men and women, ages 18 to 40, who already did some resistance training. This lifting experience was important because an effective minimalist approach should be able to continue building muscle mass and strength, even in muscles that already are somewhat strong and buff.
At first, the researchers set people’s weights so they could complete, at most, 10 repetitions of each move before they simply couldn’t manage another, a condition known as reaching failure.
Half of the volunteers continued to lift to failure every time. The other half backed off, lifting until their muscles felt challenged and tired but hadn’t reached failure; they could’ve eked out a few more repetitions, if they’d had to. Among lifters, this is known as leaving reps in reserve.
Perhaps most important for time efficiency, the volunteers completed only one set of each exercise, which, for many, represented a substantial reduction in volume. Most had been doing at least two or three sets of every exercise during their workouts, spending hours in the gym every week. Now they finished in a brisk 30 minutes.
Even a short routine can make you stronger
Even with this abbreviated routine, the participants added mass and strength, the researchers found. After two months, almost everyone’s muscles were larger, stronger and more powerful than at the start.
The magnitude of the changes proved to be similar among men and women and those who’d lifted to failure and those who’d left a few reps in reserve.
“You need to put in some effort,” Schoenfeld said. But you don’t need to lift until your muscles are completely exhausted to show significant gains in strength and size.
You also don’t need to follow this study’s regimen precisely, he said. “There’s nothing special” about these particular exercises, in this order. Substitute body weight exercises like pull-ups or push-ups for some of the exercises, he said, or ask a trainer at your gym to show you the machines there that work the shoulders, biceps, back, core and legs.
If you’re new to lifting, the trainer could be especially useful, Schoenfeld added, to teach you proper form.
But the key to lifting for muscle health will always be simple consistency, he said. Show up twice a week and challenge your muscles.
It’s unlikely, based on this study, that most of us need more than two, short weight workouts a week, he continued, unless our goal is to become swole. (Mine isn’t.)
On the other hand, we probably can’t get away with fewer than two sessions most weeks, he said, if we wish to keep growing stronger.
As for scheduling those workouts, “don’t do them back-to-back,” Schoenfeld advised. Leave at least one day between each session, but otherwise Tuesdays and Thursdays, or Fridays and Mondays, or Sundays and Wednesdays, or whatever works for you should be fine, he said.
This study was relatively short-term, lasting only eight weeks, and involved mostly healthy adults. It’s “quite likely” but not certain that the results apply equally to older people and other groups, Schoenfeld said, and that the benefits continue past two months. He plans future studies of those issues.
But for now, “the message, I think, is to find one hour somewhere in your week” to lift, he said, which can be as much — and as little — as most of us need.