It’s pretty easy to notice when your fitness or strength is declining.

Unfortunately, the same doesn’t apply for your bone health. You can’t actually feel your bones getting weaker.

Bone loss can occur gradually over years without many symptoms, and the first indication many people get that their bones have weakened is when they sustain a fracture. And the unfortunate truth is a broken bone at age 70 or 80 can have vastly different consequences to one at 20 or 30.

Beyond fractures themselves, bone loss can have broader consequences ranging from reduced mobility, loss of strength, reduced confidence, to an increased risk of hospitalisation or loss of independence.

And despite common perception, men aren’t immune to these effects either. In fact, estimates suggest 1 in 5 men over 50 will experience an osteoporosis-related fracture in their remaining lifetime.

Most people recognise the importance of exercise and particularly resistance training for improving bone health. Common advice here is that if you want stronger bones, then you need to lift heavy.

But two recent studies challenge the assumption that heavy weights are mandatory for stronger bones, and remind us of other important factors that drive improved bone health.

So let’s walk through what bones actually respond to best - and what it means for your program.

Why “lift heavy” seems to makes sense

Bone responds to mechanical loading, or the application of force.

Resistance training exposes the skeleton to forces generated by lifting external loads (i.e., weights) and contracting muscles (and their tendons) “pulling” on bone.

So the logic of more weights = more force = more adaptation makes intuitive sense, and is probably why relatively heavy resistance training is commonly recommended for improving bone health.

While there’s probably little doubt heavy lifting can be effective, the question is whether lighter loads can still be effective too.

Luckly, two recent studies help tease apart that distinction.

Heavier is better for strength, but not clearly for bone density

The first study was a systematic review/meta-analysis of 18 RCTs involving 1,283 adults aged ≥50.

Each study included in the analysis compared higher-load (≥70% 1-RM) versus lower-load (<70% 1-RM) resistance training on both strength and bone outcomes over 8 weeks to 12 months.

The main finding was that higher-load resistance training produced better strength outcomes, but there was no statistically-significant difference in bone outcomes (specifically bone mineral density or BMD) at both the lumbar spine and femoral neck.

There was a trend towards greater improvements at the lumbar spine with heavier training, so we shouldn’t interpret these findings as showing that intensity doesn’t matter. But there was no clear advantage of heavier training for BMD overall.

These findings provide an interesting contrast in that load mattered for strength, but didn’t clearly impact bone outcomes in this study.

And another recent study makes the “heavy is better for bone” argument even less straightforward.

Moderate loads can improve bone too

The second study was a network meta-analysis of 34 RCTs in 1,746 middle-aged and older adults lasting between 8 weeks and 3 years.

Each included study compared different combinations of resistance-training frequency and intensity, with intensity (load) categories of:

• Low (≤65% 1-RM)
• Moderate (65–80% 1-RM)
• High (≥80% 1-RM)

The key finding was moderate-load resistance training performed 3 times per week ranked highest for several key bone (specifically BMD) outcomes including the lumbar spine and femoral neck. That means the analysis ranked this frequency and intensity combination as the “best” for these bone outcomes.

But, this shouldn’t be interpreted as an optimal prescription for bone health - because as the authors acknowledge, there were substantial differences between the interventions used across studies, and the certainty in the findings was generally low or very low.

A better conclusion is that moderate-load resistance training appears to be a perfectly viable option for improving bone health - and there was no clear evidence here that lifting ≥80% 1-RM was superior.

So, do you need to lift heavy?

It’s an annoying answer…but yes and no.

You probably need to lift heavy enough, but that doesn’t mean you need to lift very heavy.

These studies don’t suggest there is a linear relationship between load and bone outcomes, or “the heavier the better”. Rather, something around the 65-80% 1-RM range seems like a reasonable ballpark based on the available evidence.

That doesn’t mean lifting heavier is a bad idea either - when appropriately prescribed and supervised. In fact it makes sense if your goal is also to maximise your strength.

But the bigger problem with focusing on “how heavy” is load is only one part of the mechanical stimulus bones experience. Bone adaptation is highly site-specific, and it respond to characteristics of loading that go beyond just the weight on the bar.

So instead of asking “how heavy should I lift?”, the better question is:

“How can I expose my bones to the right kinds of loading?”.

#1: Make it CHALLENGING (enough)

If you want to improve bone health, resistance training loads should be challenging enough.

These papers suggest that might be somewhere in the ballpark of 65-80% 1-RM.

But despite this, I wouldn’t obsess over percentages.

The goal should be to progress towards loads that are heavy enough, without feeling like every lift needs to be extremely heavy.

#2: Make it TARGETED

Bone adaptations are very site-specific.

Which means only the parts of the skeleton that are loaded by specific exercises will benefit.

So, think about the priority areas. For example, if bone density of the hip or spine matters, then the exercises you do should load those regions (in a safe way).

That might include exercises like:

• Squat/leg-press patterns
• Split squats/lunges
• Hip hinge/deadlift patterns
• Loaded carries

Just because an exercise provides enough “load” doesn’t mean it’s good for bone health in the areas that might matter.

#3: Make it VARIED

Bone seems to get “bored” quite easily.

Because in addition to responding to sufficient load, bone also likes different types, rates, and directions of loading.

So depending on your physical ability and risk profile, this could include things like:

• Jumping
• Hopping
• Multidirectional movements/landings

That’s why some of the more evidence-based programs for bone health may be the combination of moderate-to-heavy resistance training combined with short bouts of impact activity and mobility or balance work.

This provides the skeleton with loading stimuli that resistance training alone may not always provide.

#4: Make it CONSISTENT (over time)

One of the challenges of bone health, and understanding what improves it, is that it doesn’t respond quickly.

While you can notice improved strength within weeks after starting training, bone might take months to years to respond.

Which is why it’s important to play the long game here. The goal is to progressively load your bones in an appropriate way over months to years, rather than chasing the perfect intensity.

The right approach for you should be something you can continue doing for a long time, so don’t make it any more complicated than it needs to be.

So, do you need to lift heavy for stronger bones?

These latest studies suggest the answer is somewhere in between:

You need to lift heavy enough, but heavier is probably not always better. Even moderately heavy loads seem to be beneficial for bone, as well as for strength.

But bone health is about more than just load.

Getting the right kinds of loading - challenging enough, but also targeted and varied - and doing it consistently over time is probably what matters most.

And remember - bone health is more than what builds stronger bones. It’s also about reducing the risk of fractures and maintaining the physical capacity and independence our bones help support.

Which is another reason resistance training remains one of the best investments we can make in staying strong, capable, and independent as we get older.

Hope you enjoyed this!

Until next week,

Jackson

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IMPORTANT:

The information contained herein is of general nature only and does not constitute personal advice. You should not act on any information without considering your personal needs, circumstances, and objectives. Any exercise program may result in injury. We recommend you obtain advice specific to your circumstances from an appropriate health professional before starting any exercise program.