So, you want to lift weights but aren’t sure where to start. You scroll through your Instagram feed looking for guidance – but all you see are fitness influencers touting the idea you either lift big or don’t bother.

That’s a bit intimidating and disheartening, right? But as with most things exercise and health, it’s not really that simple.

I’m an exercise scientist (and former Commonwealth powerlifting medallist and national Olympic weightlifting champion) who researches resistance training, also known as lifting weights. Research suggests lifting smaller weights and doing more repetitions (or, in gym parlance, “reps”) can have a role to play – but it all depends on your goals.

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

Hang on: what do we mean by ‘heavy’ or ‘light’?

What’s heavy for one person may be a piece of cake for another.

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

The more reps we do, the less accurate the relationship. But some estimates predict you could do approximately 20 reps at 60% of your one repetition maximum (of course, it varies depending on the person).

It’s worth remembering not everyone can lift heavy, perhaps due to age, injury or just being new to the gym. And perhaps while you are unable to lift heavy now, it doesn’t mean that will always be the case. But the key thing is this: if you’re going to train at a lower intensity, say 40% of your one repetition maximum, you’ll need to do a lot of reps to have a positive benefit.

The benefits of lifting heavy

Lifting loads ranging from 40% to 80% of your one repetition maximum has been shown to elicit improvements in muscle mass (hypertrophy). However, research also shows lifting at higher loads is needed to maximise improvements in muscular strength.

High-intensity exercise is probably the most effective type of exercise for maintaining and improving bone health. Research has shown the best approach for bone health is to combine high-intensity resistance and impact training.

Lifting lighter? Here’s what you need to know

Research has shown participation in high rep, low intensity BodyPump™ classes may offset age-related reductions in lumbar spine bone mineral density. If you choose to lift lighter weights, you’ll need to do more reps to get the same benefits lifting heavy would yield.

Research also shows if you’re lifting lighter, muscular failure is likely required to elicit muscle growth. In other words, you likely need to lift all the way until exhaustion. Lifting heavy may get you the same benefit without needing to go all the way to exhaustion.

What about burning energy?

On average, a one-hour low-intensity/high-rep style resistance training session may burn about 300 calories. A heavy session with longer rest periods equates to roughly the same calorie burn as a higher rep session with less rest.

There may also be sex differences in the way in which older men and older women respond to resistance training. For example, older men may benefit from higher-intensity programs, whereas older women may actually benefit from higher-volume programs (more repetitions).

It’s worth noting that low-load training is hard. It’s actually really uncomfortable to do low load/high rep training to failure, or close to it (remember: “training to failure” means getting to a point where you actually cannot do any more lifts). It requires a significant degree of motivation and willingness to tolerate discomfort. Doing low-load training without serious effort is unlikely to result in significant improvements in muscle growth and strength. So, if you choose this style, make sure you are ready to put in the effort.

Benefits of light weights include the fact they are portable, meaning you can work out in a pleasant environment such as the beach, the park, or while on holiday. They don’t cost as much and are easy to store. For many, they are also not as 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 advantages of more traditional heavy-weight training.

It depends on your goal

The moral of the story? It does matter what you do, and how you do it. But, probably not as much as you think. If an influencer or fellow gym-goer is saying their way is the only way, question it with healthy scepticism. They are not you, they do not have your exact goals or limitations, and there’s likely more than one way for you to achieve the outcome you’re after. 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 School of Health Sciences, UNSW.

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Lifting weights once a week linked to reduced risk of premature death – new study