So you want to lift weights but you don’t know where to start. You scroll through your Instagram feed for advice — but all you see are fitness influencers touting the idea that you either lift big or don’t bother.

It’s a bit intimidating and discouraging, isn’t it? But like most things about exercise and health, it’s not that simple.

I’m an exercise scientist (and former Commonwealth Weightlifting Medalist and National Olympic Weightlifting Champion) who researches resistance training, also known as weight lifting. Research suggests lifting smaller weights and doing more reps (or, in gym lingo, “reps”) may have a part to play — but it all depends on your goals.

In short: if your goal is to build serious strength and bone density, heavy lifting is an effective way to achieve it. But if you can’t lift heavy weights or it’s not your thing, don’t think lifting lighter weights is a complete waste of time.

Wait: what do we mean by “heavy” or “light”?

What is heavy for one person may be a breeze for another.

In resistance training, the load or “heaviness” of a weight is often expressed as a percentage of a “one rep maximum” (often abbreviated as “1RM”). A maximum of one repetition is the heaviest load you are able to lift successfully once. Around 80% of your rep max is often defined as “high intensity” or heavy lifting. Around 40% or less of your rep max is often defined as “low intensity.” In other words, lifting 80% of your one-rep max would get you about eight reps.

The more repetitions we do, the less precise the relationship. But some estimates predict that you could do around 20 reps at 60% of your rep max (of course, this varies by person).

It is worth remembering that not everyone is box heavy lifting, perhaps due to age, injury, or simply being new to the gym. And maybe even if you can’t lift heavy things now, that doesn’t mean you always will. But the bottom line is this: If you’re training at a lower intensity, say 40% of your rep max, you’ll need to do a lot of reps to get a positive benefit.

The benefits of heavy lifting

Lifting loads ranging from 40% to 80% of your one rep max has been shown to cause improvements in muscle mass (hypertrophy). However, research has also shows lifting higher loads is necessary to maximize improvements in muscle strength.

High-intensity exercise is probably the most efficient type of exercise to maintain and improve bone health. The research has show the best approach to bone health is to combine high intensity resistance and impact training.

Lift lighter? Here’s what you need to know

The research has show participation in high-repetition, low-intensity BodyPump™ classes can offset age-related reductions in bone mineral density in the lumbar spine. If you choose to lift lighter weights, you will need to do more reps to get the same benefits as lifting heavy weights.

Also research shows if you lift lighter, muscle failure is likely required to cause muscle growth. In other words, you will probably have to lift until exhaustion. Heavy lifting can give you the same benefit without having to go to exhaustion.

What about burning energy?

On average, a one hour low intensity/high repetition style resistance training session can burn about 300 calories. An intensive session with longer rest periods equates to about the same calorie burn as a higher repetition session with less rest.

There may also be sex differences in how older men and older women respond to resistance training. For example, older men may benefit from higher intensity programs, while older women may actually benefit from higher volume programs (more reps).

It should be noted that low load training is difficult. It’s actually very uncomfortable to do a low load/high rep workout to or near failure (remember: “training to failure” means getting to a point where you can’t no more elevators). It requires a significant degree of motivation and willingness to tolerate discomfort. Stock low-load training without serious effort is unlikely to cause significant improvements in muscle growth and strength. So if you choose this style, make sure you are prepared to put in the effort.

The benefits of lightweights include the fact that they are portable, which means you can exercise in a pleasant environment like the beach, park, or while on vacation. They are inexpensive and easy to store. For many, they are not so intimidating. For some, these benefits will make it easier to stick to a regular exercise routine. For others, these benefits may not outweigh some of the aforementioned benefits of more traditional heavy weight training.

It depends on your goal

The moral of the story? It doesn’t matter what you do and how you do it. But, probably not as much as you think. If an influencer or other gym-goer says their way is the only way, question them with healthy skepticism. They’re not you, they don’t have your exact goals or boundaries, and there’s probably more than one way for you to achieve the outcome you’re looking for. DM/ML

This story was first published in The conversation.

Mandy Hagstrom is a senior lecturer in exercise physiology and director of teaching and education at the UNSW School of Health Sciences.

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