Olympic swimmers have leg bones no better than people who never exercise

An Olympic swimmer trains six days a week and has done since she was eleven. Her whole adult life is exercise. Put her on a bone scanner and her legs come back about the same as women her age who do no sport at all (Bellver and colleagues).

Not close to the same. The same.

Now the cyclists. A research team scanned a professional road cycling team and found that two thirds of the riders had bone density well below the normal range (Medelli and colleagues). Not retired riders in their sixties. Working professionals, mid-season, whose entire job is their legs.

Nobody thinks these people are lazy.

So if you have recently been handed a scan result, and your first thought was that you should have done more, hold that thought loosely for the next ten minutes. It may be the wrong thought entirely.

And if you have noticed yourself changing since that result came, this is worth ten minutes for a second reason.

You know the changes I mean. You hold the stair rail now. You look at the ice on the front step and work out where to put your feet, where before you just walked out. Somebody's arms go up to be lifted and there is a half second first. You said no to the trip with the walking on it and told everyone you did not fancy it.

Nothing hurts. Nothing has actually happened. And something has still changed, and you are mostly carrying it on your own, because the word makes people picture a frail woman with a frame and you went to a spin class on Saturday.

The strongest, most disciplined, most relentlessly active people on the planet are turning up with the same scan result you got. Effort is clearly not what separates them from anybody else. So it is worth finding out what does.

Four things this piece explains:

• Why an Olympic swimmer's legs scan like somebody who has never exercised
• What your bones are actually counting, which is not minutes and not effort
• The trial that broke the rule about heavy weights and thin bones, run on the women the rule was written to protect
• Eight things to do about your own scan report, every one of them free

Different countries, different sports, the same hole

One study is a curiosity. Here is the rest of it.

• Two thirds of a professional road cycling team had bone density well below the normal range (Medelli and colleagues).
• Female Olympic swimmers measured no better than the women who did no sport at all, who were used as the comparison group (Bellver and colleagues).
• Ten of nineteen elite Norwegian endurance cyclists had low bone density. One of them, an elite athlete, had osteoporosis (Andersen and colleagues).
• Road cyclists show osteopenia at about 63 percent, against about 19 percent in runners. The authors put the difference down to cyclists carrying roughly half the loading history of runners.
• One study measured swimmers 9.8 percent lower in the bones of the legs than people who did no exercise at all.
• In that same study, the endurance swimmers came in 14.8 percent lower.

Different countries. Different sports. Different research groups, working separately, some of them years apart. The same hole in the same place.

Two caveats, and you should hear them from me rather than find them yourself later. Most of those athletes are men, and most of them are decades younger than you. None of those studies was designed to tell a sixty year old woman what to do on a Tuesday morning.

What they are is the cleanest accidental experiment anyone has ever run. Take thousands of hours of the most demanding physical work a human body can do, remove one specific ingredient, and watch what happens to the skeleton. Nothing happens to the skeleton. That tells you the missing ingredient is the whole story.

Your skeleton is a thermostat, and nobody was setting it

Bone is not a rock. It is not scaffolding that got built when you were twenty and has been quietly crumbling ever since.

It is living tissue, and it is being torn down and rebuilt continuously, your whole life, by two crews of cells working against each other. One crew removes old bone. The other lays down new. Whether you gain or lose comes down to which crew is winning this year, and something has to decide that.

In 1987 a doctor named Harold Frost worked out what does the deciding.

His model says bone measures the strain passing through it, and it only adds material when that strain crosses a threshold (Frost, 1987). Below that threshold it does the opposite. It quietly sheds material it has no evidence you need.

Think of the thermostat in your hallway. It sits there doing absolutely nothing while the room drifts about. Then the temperature crosses a set point and it acts. Your bones work the same way. The thing they measure is force.

And this is the part that changes how the whole thing feels: that is not your body malfunctioning. Bone is expensive. It costs minerals, it costs blood supply, and you have to carry every gram of it around all day. A skeleton that keeps material it has no evidence you need is a skeleton wasting your resources. So it doesn't. It is being efficient, using the only information it has, which is the force you send it.

Nobody sent it any force.

Why the pool and the bike are the worst offenders

Water holds you up. That is the entire appeal of swimming, and it is exactly the problem. Once you are in the pool the water carries most of your body weight, so very little force travels through your hips and thighs no matter how hard you work. The muscles get a superb session. The skeleton gets almost nothing.

On a bicycle the frame carries you. You sit on it. Your legs push against pedals that turn smoothly, and there is never a landing, never a jolt, never a moment where a big force arrives fast. Cyclists can work at the limit of human endurance for five hours and their bones see less force than a person walking to the shops. That is why the cycling numbers look so bizarre until you know about the threshold, and completely sensible afterwards.

Yoga is mostly your own body weight, moved slowly, and your body weight is the load your skeleton has already adapted to. That is what "already adapted" means.

And walking. Walking does load your legs, but it loads them at roughly the level your skeleton already meets every day getting around the house, which puts it at your current set point rather than above it. It is the baseline. You cannot use the baseline to move the baseline.

Somewhere along the way the phrase "weight-bearing exercise" came to mean "on your feet". That is where the advice went wrong, and it went wrong in a way that sounds completely reasonable, which is why it has lasted. Your bones are not counting whether your feet are on the ground. They are counting how much force arrives, and how fast.

There are only two ways over the line. Something heavy, moved by you. Or something fast, landing through you. Everything else is exercise, and exercise is good for a great many things that are not this.

One thing nobody can hand you: your own threshold as a number. There is no scan, no watch and no formula that reads out the exact weight at which your hip decides to start building. Anybody quoting you that number invented it. What exists instead is a trial that found the level empirically, in women your age, and I will get to it in a minute.

Which means the question was never how much exercise you did. It was whether any of it ever crossed the line.

The four things health-conscious women actually do

Now the part that lands hard, and I am going to say it anyway.

Cycling. Swimming. Yoga. Walking.

Those four are, by a distance, what health-conscious women between fifty and sixty-five actually do. They are the four things a doctor suggests, the four things that are easy on the knees, the four things with a class and a group and a friend attached. All four sit at or below the threshold. As a signal to bone, all four are close to zero.

I know exactly what that sentence costs to read.

Thirty years of Tuesday mornings. The pool in February when the car park was still dark. The bike you saved for. The hip that ached and you went anyway. You did not skip it when it rained, you did not skip it when work was bad, you did not skip it the year everything else fell apart.

And it did not build your bones.

You did not fail at this. You followed the instructions you were given, faithfully, for decades, and the instructions were wrong. Those are different things and I need you to keep them separate, because the woman who believes she failed usually stops, and stopping is the only genuinely bad outcome available here.

Here is what I am not saying. I am not saying those years were wasted, and I would fight anyone who tried to tell you they were. Your heart, your blood pressure, your weight, your sleep, your mood and your balance all got something real out of that work, and the balance matters enormously here, because almost every hip fracture needs a fall first. Keep the class. Keep the group. Keep the bike.

They were just never going to pay this particular bill. Nobody mentioned there were two bills.

If you are angry reading this, be angry at the advice. Not at yourself, and not at the doctor who repeated it, who was reading the same guidance as everyone else.

Menopause did not cause this. It stopped hiding it.

And then menopause arrives and gets blamed for the whole thing.

Estrogen holds back the cells that break bone down. While you had plenty of it, your skeleton could get away with receiving almost no mechanical signal, because the demolition side was being restrained anyway. When estrogen falls, that restraint comes off and the losses arrive quickly.

Menopause did not cause the loss. It removed the buffer that was hiding thirty years of it.

The number on your report is not a photograph of the last five years. It is thirty years of a signal that never arrived, finally showing up on a page, at the exact moment the thing covering for it stopped.

Then a research group tested the rule everybody was obeying

In Queensland, a group of researchers went and did the thing that everyone had spent twenty years saying must never be done.

The rule was simple and it was everywhere. If a woman has thin bones, keep her away from heavy weights. Give her light bands, water aerobics, a walking group. Above all do not put a loaded barbell across her back or in her hands. She will break.

Belinda Beck's group at Griffith University decided to actually test that, and they tested it on the exact women the rule was written to protect. Not fit fifty year olds with good scans. Women who already had the diagnosis.

They took postmenopausal women with low bone mass, including women with osteoporosis, and had them deadlift, squat and press overhead at five sets of five, at more than 85 percent of the heaviest weight each woman could lift once, twice a week, thirty minutes a session, for eight months (Watson, Weeks, Weis, Harding, Horan and Beck, 2018). The trial is called LIFTMOR. The comparison group did a low intensity home program, which is roughly what most women get told to do.

The heavy group gained bone density in the lower back and at the top of the thigh bone, where it goes into the hip. That second one is the break that ends people's independence. A second analysis of the same trial found the training did not break any bones in the spine, and reported that the forward curve of the upper back got better.

Thirty minutes, twice a week. Add it up. One hour.

Two things about that trial, and they pull in opposite directions

One is the size of the result. The other is the room it happened in.

The size first. The spine gain was in the region of 3 percent over eight months. In this field that is a genuinely good result. It is also a small number, and you want it from me now rather than from a radiologist in two years. This is slow work on a slow tissue. Anybody promising you a dramatic scan has not read the paper.

The second matters more. Every woman in that trial had a trained supervisor standing next to her, for every set, for eight months. Their weights came off a proper test of the heaviest they could lift once. None of that is available to a woman in her garage on a Wednesday night with a phone propped against a shoe.

So the trial tells you what the signal has to look like. Getting near it without a coach in the room is a second problem, and it gets solved with design rather than optimism. A month of technique before any real load. Effort ratings instead of percentages of a maximum you should never go hunting for alone. A filmed self-check that has to pass before the weight gets serious. And a hard screen up front that tells some women no: a broken bone in the spine, any break in the last two years, a T-score of -3.0 or below, spinal stenosis, and a short list of others. Those women get sent to their doctor rather than to a barbell.

That gap, between a supervised trial and a woman alone in a garage, is the whole job. When somebody tells you their program is LIFTMOR, they have either not read it or they are counting on you not having read it.

Eight things to do about your own report, all of them free

You do not have to buy anything to act on this. Most of what follows is free and some of it is more useful than anything I sell.

1. Get the actual report, not the sentence. Most women are told "you have osteopenia" and never see the page. Ask for it. You want the g/cm² figures, not just the T-scores, and you want to know which parts of you were scanned and which bones went into the spine average.

2. Write down where you were scanned and on what machine. Different scanners are calibrated differently, and a comparison across two of them is not a comparison at all. When you go back, same facility, same machine, ideally the same technologist. A hip positioned five degrees differently can move your number more than a hard year of training will.

3. Ask the clinic a question they will not expect: how much do your own scans vary when you scan the same person twice? A good unit knows its own number. A unit that has never worked it out has just told you something useful about how much weight to put on their next result.

4. Do not book the rescan too soon. Bone rebuilds slowly, and at twelve months the change is usually too small to tell apart from the wobble in the machine. Twenty-four months is the better bet unless your doctor has a specific reason to look sooner, and sometimes there is one.

5. Have the conversation about the things that are not exercise. Medication, vitamin D, calcium, protein, alcohol, whether anything else is quietly driving the loss. That conversation belongs to your doctor, not to me, and I have an obvious interest in you deciding that lifting is the answer to everything.

6. Stop counting minutes. Start asking whether anything was heavy. This is the single cheapest change available to you. At the end of a week of activity, ask one question about it: did my skeleton experience anything today that it does not experience getting out of a chair? Most weeks, for most people, the honest answer is no.

7. If any of these apply to you, ask before you load anything. A broken bone in your spine at any point in your life, including one somebody found by accident on an X-ray. Any fracture in the last two years. A T-score of -3.0 or below. Spinal stenosis or spondylolisthesis. Blood pressure that is not under control. Surgery in the last six months. This is not a formality. It is the specific list where doing this alone is the wrong call, and every item on it is there because of how bone fails rather than because of how paperwork works.

8. Whichever way you go, stop doing sit-ups and standing toe touches. Bending forward with weight in your hands puts the force on the front edge of each bone in the spine, which is exactly where a thinning spine gives way. Sinaki and Mikkelsen reported far more broken bones in the spine among postmenopausal women doing forward-bending exercise than among those doing backward-bending exercise (1984). That paper is from 1984 and the advice still has not fully reached the aerobics floor.