Think Lifting Heavier and Heavier Is the Only Way to See Results? Science Says Otherwise

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Scroll any fitness feed and you’ll see it: people clanging plates, chasing PRs, and even pulling dangerous stunts for the pride of lifting heavy. And where there’s real joy in getting stronger, there’s also real pressure to keep adding weight.

As a strength and conditioning coach and the fitness editor at Women’s Health, I’ve been preaching the lift-heavy-or-go-home gospel for years. For valid reason: challenging your muscles over time is one of the most reliable ways to build lasting strength, support bone health, improve body composition, and stay functional as we age.

The “lift heavy” ethos isn’t new. Strength training is as old as Ancient Greece, where the first gyms were developed. It progressed through decades of physical culture into Muscle Beach, USA, the birthplace of American lifting that started as a beachside gymnastics park in Venice Beach, California, in the 1940s. It was there, too, where the first American women bodybuilders, like legendary Abbey Stockton, emerged—at a time when many scientists still believed lifting was bad for the body.

Research eventually caught up to what lifters were already experiencing: resistance training works. More women, especially in recent years, started showing up for it, too. In 2004, 17 percent of women reported regularly participating in weight lifting. By 2020, that number has bumped to nearly 30 percent. Then came the influencer era, amplifying a message that’s equal parts motivating and misleading: lifting weights is good for you—but it has to be heavy to count.

There’s a kernel of truth in there. Progressive overload (the process of gradually increasing the stress you put on your body in a workout) builds muscle and strength, and increasing load is an efficient way to do so.

Still, the science has moved beyond a simple “go heavy or go home” mentality.

And that matters—especially when heavier, heavier, heavier simply isn’t in the cards.

Because for many, it’s not. It requires access to specific equipment, time to train consistently without rushing through sets, and quality coaching and information to nail form and stay injury-free. It also has to be safe and appropriate for your body on any given day—whether you’re navigating chronic illness, postpartum or perimenopause realities, and injury history, or limiting pain. And even when everything lines up on paper, there’s a very real mental hurdle: walking into a gym and loading up a bar can be intimidating as hell.

Still, if you’re here to build strength, change your body composition, protect your bone health, or invest in your movement longevity, lifting heavier will certainly help—but it’s not the only path to lifelong strength. Somewhere along the way, “heavy” became synonymous with “effective”, and “light” or “moderate” became codes for “waste of time.”

The exercise research world is finding that’s not the case. “You don’t need to do anything heavy for the health benefits of resistance exercise to take place,” says Stuart Philips, PhD, kinesiology professor and hypertrophy researcher at McMaster University.

The new rule of strength is simpler and more personal: train close to fatigue, whatever that feels like for you.

Adequate research has suggested that hypertrophy (the fancy scientific term for muscle growth) is not determined by a magic rep goal or the weight on the bar, says Susie Reiner, PhD, CSCS, is an exercise physiologist, assistant professor of exercise science at Seton Hall University, and CEO of TheoryEx, a sport science research and consulting firm. “Instead, hypertrophy appears to be driven by whether a training set provides a sufficiently strong internal stimulus to the muscle, which is reasonably defined as effort and proximity to muscular failure.”

Trainers have traditionally been taught that specific rep ranges map neatly to specific goals: 1 to 3 for power, 3 to 8 for strength, 8 to 12 for muscle, and 12-plus for muscular endurance. But newer findings show you can build muscle across a much wider rep range—roughly as low as 5 and as high as 25, Philips says. “There is, then, by definition, no sweet spot for muscle building, because the whole repetition range then becomes the sweet spot.”

Across several studies and meta-analyses, similar muscle growth has been seen between people who train with lighter loads (about 30 to 40 percent of their one-rep maximum), and those who train with heavier loads (about 70 to 85 percent of their one-rep maximum)—as long as sets are taken close enough to failure.

Muscle growth is dependent on recruiting and fatiguing a large portion of muscle fibers, Reiner says. Your muscles need a reason to adapt. With heavier weights for fewer reps, you recruit a lot of fibers immediately. With lighter weights for higher reps, you recruit them more gradually.

One thing to note here: while a large percentage of these studies have only been done in men, Philips notes that “the work that has been done in women shows us that actually men and women respond very, very similarly to weight lifting in terms of muscle mass gain. Women have less baseline muscle, but relatively speaking, they gain the same amount as men—that’s been robustly shown.” Philips and his colleagues are currently running several studies (including one study specific to perimenopausal women!) that will further clarify what this looks like in women.

Researchers feel confident that as long as sets are taken sufficiently to failure (more on what that means coming up), different loading strategies can produce similar hypertrophy, Reiner says.

Here’s what that looks like IRL: Let’s say you have biceps curls on your workout plan each week. One week, you pick up the 10-pound dumbbells, and do 3 sets of 12 reps. In the sets, when you approach the end of that rep range, it feels tough—you can maybe grind out 2 more reps max. The next week, you reach for the 15s. You can only hit 6 reps before you feel like your form is faltering, but the effort feels similar—you’ve still got about two reps left before your form breaks down.

The heavier weight might feel more empowering, but both workouts deliver a similar muscle-building stimulus—assuming you’re training regularly enough, eating enough protein and calories, and adequately recovering, of course.

However, you don’t need to reach absolute failure.

Sure, research confirms you don’t have to lift crazy heavy—but that doesn’t mean that coming close to failure feels easy. Failing a rep can be scary (and honestly, discouraging). Here’s the good news: you don’t need true, all-out failure. You just need to train to proximity to failure.

One practical way to gauge that is with the rate of perceived exertion scale. “Rate of perceived exertion (RPE) is a global effort scale, typically ranging from one to 10,” Reiner says. An RPE of 10 represents maximal effort—no chance you could do one more rep. A RPE of nine suggests you could do one more, an RPE of eight means you could probably do two more reps, and so on and so forth.

Muscle growth still occurs between RPE of 7 to 9, Stud says. “You don’t need it to be a 10 out of 10 where you’re red-lining and can’t get the bar off your chest.” In other words: you can train hard without routinely hitting the point where things get sketchy.

That matters, because the closer you get to all-out failure, the more your injury risk can creep up—especially if you start twisting, bouncing, and compensating to force a rep you simply don’t have.

There are two different kinds of failure: muscular failure and technical failure.

The failure you want to flirt with is technical failure, or technical fatigue. “Technical failure means you cannot complete another repetition with good form,” Philips says—that’s where injury risk rises. Muscular failure (otherwise known as momentary failure) occurs when a muscle is unable to generate enough force to complete another rep, regardless of maximal effort. Picture trying to do one more biceps curl and you quite literally cannot lift your arm and the weight up again—that’s muscular failure..

Aim for technical failure. Pushing yourself too far in an effort to achieve muscular failure could cause your body to overcompensate and push you into a compromising position. The good news, too, is technical failure tends to be very close to muscular failure for most people, Philips says.

A useful rule of thumb: stop when you have one to two perfect-form reps left in the tank.

Try these other ways to challenge your muscles, too.

Yes, you still need to reach for that RPE of 7 to 9—but there’s more ways to do that than just reaching for the next highest weight. Here are some other elements you can play with to up the challenge:

Frequency. Reaching for heavier weights, you can simply aim to reach for any type of weight more often. That might look like increasing your strength training days from two to three days a week.

Volume. Think of your training volume as the amount of weight total you lift during a given session. Sure, lifting heavier loads is one way to increase your total, but it can also be accomplished by increasing the amount of sets or reps you do.

Rest time. Decreasing the amount of rest you allow yourself gives your muscles less time to recover, wearing them out quicker with lighter loads.

Time under tension. The amount of time your muscles work for matters. Increasing your time under tension, or the amount of time your muscles are working in a lift (for example, lowering a curl for a slow four-count).

That all being said, heavier loads might still take the cake in terms of efficiency. You’ll find yourself increasing your frequency and volume to monotonous levels if you never increase your load.

Back to biceps curls: Say you get comfortable at six reps at 15 lbs. After a few weeks, it no longer starts to feel challenging for you, so you increase it eight. And then 10. And then 12. If you never reach for the intimidating 20 lb dumbbells, you’ll eventually find yourself having to do sets of 30 reps just to feel something. And that can become time consuming. You don’t need extremes all the time—but you do need your training to stay challenging.

“For individuals who are uncomfortable training to very high levels of effort, consistent training at moderate-to-high RPEs combined with sufficient volume and progression can still produce meaningful muscle growth,” Reiner says. “From a long-term perspective, hypertrophy depends less on any single maximal set and more on repeated exposure to challenging, well-managed training over weeks and months.”

How to Increase Your Load Safely

Convinced to start pushing closer to failure? Here are a few ways to progress safely.

Use the Two-for-Two Method

The two-for-two method is a classic progression strategy used by professional trainers. Once you can do two extra proper-form reps beyond your planned rep target for two workouts in a row, you’re ready to increase your load.

Let’s use the biceps curl example just one more time. You’ve been training with the 15s for sets of 8, and now you can hit 10 with clean form for two workouts in a row. That’s your cue to grab 17.5s the next go.

How much should you increase, exactly? The National Strength and Conditioning Association’s guideline is 2.5 to 5 pounds for upper-body exercises, and 5 to 10 pounds for lower-body exercises. Reminder that this is just a general guide—you can do more or less based on how you specifically feel.

Ask for a Spot

Trying heavier weights is way less intimidating when you have a safety net.

If you’re nervous, ask for a spot. Maybe you already have a gym buddy you workout with regularly that can help pull the barbell up if you get stuck on a bench press. If you don’t, ask one of your gym’s trainers or employees. Most people will politely oblige, and will even appreciate your effort in challenging yourself.

Have a conversation with your spotter before you get into the lift. Tell them how many reps you’re aiming for, and a cue you’ll give them when you want them to jump in and help (my go-to is a simple “now”—since that’s about all you can get out when you’re out of breath).

Respect Your Body’s Cues

Some days just don’t feel as strong as others. Maybe you didn’t sleep super well last night, stressed about work, or are at a tough point in your cycle. That’s life. When that happens, you need to respect the cues your body gives you.

If your warmup sets feel unusually heavy, take the hint: this just might not be the day to pick up that heavy weight. It doesn’t mean you’ve regressing, it’s just a bump in the road. Strength, and muscle building, is not a linear process.

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The takeaway: progressively challenging yourself matters more than the load itself.

Ultimately, building and maintaining muscle mass is one of the strongest investments you can make in long-term health—especially as you age.

And lifting heavy is one effective way to provide muscle-building stimulus to the body—but it isn’t accessible, comfortable, or safe for everyone all the time. The goal is progressive challenge, and lighter loads can deliver that when you train with intention and effort.

“You do not need to lift heavy to build muscle, but you do need to train with intention,” Reiner says. “The best approach is the one that someone can perform consistently, safely, and with enough effort to challenge the muscle over time.”