Should You Lift Light Weights for High Reps or Heavy Weights for Low Reps?

We all got the memo: After the age of 50, strength training is more important than ever. But the best method for maintaining muscle mass still seems to be up for debate.

Should you crank out lots of reps using light weights, or is it better to do fewer reps with a heavy load?

The exact answer depends on your goals and current fitness level, but some general guidelines help take the guesswork out of your next workout.

Why Strength Training Is So Important After 50 and How to Figure Out Your Goal

Sarcopenia, or age-related muscle and strength loss, begins around age 35 and accelerates over time. By the time you hit your 50s, you could be losing one to two per cent of your muscle mass and strength with each passing year.

“That can affect more than just how we look,” says Hilary Granat, a physiotherapist specialising in menopause and midlife fitness. “It can affect balance, mobility, bone health, metabolism and even our ability to perform everyday activities.”

These changes often coincide with a dip in activity, as people in their 50s may no longer be chasing around young children, playing sport or socialising as much as they did in their 30s and 40s. An increasingly sedentary lifestyle can compound the negative effects of sarcopenia and contribute to weight gain, osteopenia and osteoporosis, and other health issues.

Staying active helps slow this decline, but it’s not enough to just walk a lot or do your favourite cardio workout. “If you want to have muscles as you age, lifting weights isn’t optional,” Hilary says. “It’s one of the most important things you can do to protect your strength and independence.”

“The whole reason for strength training is to initiate protein synthesis,” explains Pete McCall, a personal trainer and author of the Substack Strength Training for Longevity with Pete McCall. Muscle protein synthesis is the body’s process for repairing and building new muscle tissue, and the stress of pulling or pushing against the external resistance of, say, a loaded barbell is what stimulates that process.

“If you stop applying that mechanical tension [to your muscles], your body will stop repairing,” Pete says.

In other words, when it comes to muscle mass, you either use it or lose it. And to maintain and build muscle mass – as well as strength and independence as you age – you need to step outside your comfort zone and lift a weight that, over the course of your set, feels difficult to lift. Translation: You need to lift a weight that feels heavy for you.

What Does “Heavy” Mean and What Are the Benefits of Lifting Heavy?

The terms ‘light’ and ‘heavy’ aren’t especially helpful when choosing your load, as they’re relative not only to the person who’s lifting but also to the exercise itself. For example, a dumbbell that feels heavy for a biceps curl will seem much lighter during a goblet squat, because the quads, hamstrings and glutes are bigger and stronger than the biceps. “It’s more about effort than the actual weight,” Hilary says.

But if you want to gain or maintain strength and muscle mass, you need to lift a weight that challenges you, specifically. The last couple of reps in your set should feel nearly impossible, but you should still be able to finish them with proper form. This is a sign that you’re applying enough stress to your muscles and the systems that power them to trigger muscle growth.

“Things to look for [that signal a weight is heavy enough] are the speed of the movement slowing down, needing to produce more effort by the end of the set than at the beginning and requiring rest between sets,” says Natalie Ribble, a strength and conditioning coach. All of these indicate that you’re lifting an appropriately heavy load. “If you can quickly move from one exercise to the next, the weight might not be heavy enough,” she says.

Keep in mind that your ‘heavy enough’ weight will change as you become stronger. One way to keep making progress is to steadily increase the load you’re lifting. (This concept is known as ‘progressive overload.’) So, for example, once the 5kg dumbbells no longer fatigue your muscles in 12 reps, switch to the 7.5kg weights for six reps.

Hilary explains that your time under tension, or the amount of time the muscle is actively engaged during a set, should be between 20 and 70 seconds if you want to build strength and muscle mass. This aligns with Natalie’s general recommendation to do six to 12 reps per set (typically for two to three sets). If you’re easily exceeding 12 reps within that time frame, you’re probably not lifting heavy enough.

If you lift for longer than 70 seconds, you’re focusing more on muscle endurance – or the muscle’s ability to repeatedly contract over an extended period of time – than strength and hypertrophy (muscle growth). Muscle endurance is important, especially for activities like walking, running, cycling or swimming. And the smaller muscles that stabilise your core and support your posture need endurance to keep you upright for hours on end. But if you want to counteract muscle loss, lifting light weights for lots of reps isn’t the most effective approach.

Loading the skeletal system with a relatively heavy (for you) weight can help you preserve bone mass, too. The UK’s Royal Osteoporosis Society recommends doing eight to 12 reps with a weight heavy enough that you may need a short rest before attempting your next set. “If you are able to do 12 repetitions of the exercise and feel you can keep going, try a heavier weight,” the organisation’s website states.

This type of strength training, along with load-bearing exercise and a healthy diet, can help prevent and minimise age-related bone loss. However, if you already have osteoporosis, osteopenia, bone fractures or a history of falls, definitely check with your doctor before starting a strength-training routine, as they can provide personalised guidance for getting started safely.

Benefits of Lifting Heavy (for You) Weights for Lower Reps:

• Lifting a load that feels challenging and fatigues your muscles stimulates strength gains, which supports independence as you age.
• You’ll promote muscle growth, helping you fight age-related muscle loss.
• It’s one of the best methods for preserving bone mass and helping to prevent osteopenia and osteoporosis.

Is It Ever Better to Lift Light Weights for More Reps?

If you’re new to strength training (or getting back to the gym after an injury or a long break), doing more reps with a light weight can help you learn proper form while you get used to loading different movement patterns. Even doing bodyweight exercises, like air squats, lunges and push-ups, without any added resistance is a safe and effective starting point for a beginner.

But once you become familiar and comfortable with basic lifts, you can begin adding resistance and reducing your reps. And once that weight starts to feel easy, you need to go heavier to keep making progress.

Additionally, a lower-weight/higher-rep approach can be appropriate for exercises aimed at developing muscular endurance, motor control or stability. Pilates, for example, often uses bodyweight or light resistance to challenge the core, hip and back muscles that help stabilise the body as we move our arms and legs. “I love Pilates for improved posture, core stability and scapular [shoulder] stability,” Hilary says. “But it’s not a substitute for full-body strength training.”

Also, keep in mind that your ‘heavy’ weight for certain exercises may seem pretty light. “For example, reverse flies or some core and hip exercises may naturally use lighter loads because you’re working smaller muscles, a longer lever, or a movement where maintaining control and alignment is more important than moving a heavy load. Load is relative, and effort is what’s truly important,” Hilary says.

Benefits of Lifting Lighter Weights for Higher Reps:

• If you’re a beginner, rehabbing an injury or returning to exercise after a long break, lifting lighter weights for more reps is a safe starting point.
• Using a low-weight/high-rep scheme develops muscular endurance, which is critical for stability and good posture.
• A suitably ‘heavy’ weight for exercises that target smaller muscles may be light.

The Bottom Line on Heavy Weights/Low Reps vs. Light Weights/High Reps

Lifting light weights for higher reps can help you learn proper form and establish baseline strength. It can also improve muscular endurance in smaller, postural muscles. But to build muscle mass and strength and counteract the effects of age-related muscle and bone loss, you need to lift a load that feels heavy – and remember to keep challenging yourself so you continue to make progress.

Aim to hit every muscle group twice a week. You can do this with two full-body workouts or a combination of workouts that target specific areas of the body. If you’re not sure how to get started, consider working with a trainer or signing up for a group fitness class that focuses on strength training. “Go to the YMCA and take a BODYPUMP or strength-training class. You’ll be around other people, and you’ll have an instructor there who can give you feedback,” Pete says.

Most importantly, find a realistic routine that you can stick to. “Consistency is so big,” Hilary says, explaining that it’s far better to regularly do a couple of basic strength-training workouts a week than to jump from one fitness trend to the next or to exercise in bursts followed by long breaks.