There is a phrase so embedded in common sense that we barely notice it anymore: use it or lose it. We say it about languages, skills, friendships. But it turns out it is also a fairly precise description of what happens to the human body when we stop moving. And the science behind movement and ageing has been accumulating for a long time.
A doctor, a dataset, and a name for something we already knew
In 1984, an American physician called Walter Bortz II published a paper with a simple idea at its centre. He said that the effects of not moving enough were so consistent and so connected that they deserved a name. He called it the disuse syndrome.
His observation was that inactivity didn’t just cause one problem. It caused many, all at once. A weaker heart. Softer bones. Heavier bodies. Low mood. Bodies that aged faster than they needed to. These things showed up together, reliably, in people who weren’t moving enough. And Bortz argued that our increasingly sedentary lives were quietly driving a great deal of human suffering.
The good news, he said, was that the effects were both preventable and reversible. The treatment was movement. Cheap, safe, and available to almost everyone.
The research goes back further than that
Bortz was naming something that researchers had been circling for years. The story of how medicine came to understand the harm of inactivity is, in its own way, a story about war, gravity, and the limits of rest as a cure.
For much of the nineteenth century, bed rest was prescribed for almost everything – from tuberculosis to heart disease to post-surgical recovery. Stillness was equated with healing. The body, the thinking went, needed to be protected from the strain of movement while it repaired itself.
It was the Second World War that began to unravel this assumption. Out of sheer necessity – too many injured soldiers, not enough beds – military doctors began encouraging men to get up and move sooner after injury than was customary. What they noticed was striking. Those who moved earlier tended to recover faster, not slower.
Then came the space race. In the 1960s, as scientists studied what happened to astronauts’ bodies in the absence of gravity. And they found something disturbing. The effects of weightlessness and the effects of prolonged bed rest were remarkably similar. Muscle wasted, bone thinned and the cardiovascular system deconditioned. The body, deprived of the ordinary demands of moving through space, began systematically dismantling the capacity it no longer needed.
This research laid the groundwork for Bortz’s synthesis in 1984. By the time he wrote it, the evidence was already substantial. What was missing was a frame.
What actually happens when we stop moving
The body is a very clever system that responds to demand. Muscle fibres strengthen when they are loaded and atrophy when they are not. Bone density is maintained by the mechanical stress of weight-bearing activity. The cardiovascular system builds capacity in response to sustained effort. Even mood and cognition are shaped, in part, by physical activity. The links between movement and mental health are now well-established in the research literature.
Inactivity does not simply leave the body unchanged. It actively triggers a process of reduction. The body reads the absence of demand as information: we no longer need this capacity. And it responds accordingly.
But it is not irreversible. That is one of the most important things Bortz emphasised. The same responsiveness that drives disuse-related decline also drives recovery. The body that has lost condition through inactivity can, with consistent movement, begin to rebuild it.
Ageing, or disuse?
One of the more provocative ideas in Bortz’s paper – and in the broader literature that followed – is the question of how much of what we call ageing is actually the accumulated effect of decades of insufficient movement.
This is not a claim that ageing is simply a lifestyle problem, or that movement is a cure for the passage of time. But the research does suggest that some of what we accept as inevitable age-related decline like loss of strength, reduced balance, cardiovascular fragility, low mood, cognitive changes, overlaps significantly with the profile of disuse. And that the distinction matters, because disuse, unlike ageing, responds to intervention.
How much of the stiffness, the fatigue, the sense of the body becoming unreliable, is time? And how much is simply that we have been sitting still?
Yoga for healthy ageing
This is one of the things I find compelling about yoga as a practice. It is a sustained, intelligent relationship with the body over time.
A yoga practice asks the body to do the things that disuse gradually undoes. To bear weight, to move through range, to stabilise, to breathe, to be present in physical experience. And it does this in a way that can be adapted across age, capacity, and circumstance.
For older adults in particular, regular yoga offers something that the research consistently points to as protective: varied, weight-bearing, balance-dependent movement, practised consistently over time.
So, if you have been moving less than you’d like to – whether that’s because life got busy, because something hurt, or simply because the habit slipped away – it is not too late!
I offer yoga classes in Streatham for people who want to move more and better.
If you’re curious about classes or would like to know more about what I offer, you’re very welcome to get in touch or find out more here.
