"Sit up straight." "Shoulders back." You've heard it a thousand times, or said it a thousand times to someone else — a child, a parent, a grandparent. And more often than not, the correction doesn't last five minutes. The explanation isn't a lack of effort, and it isn't weak muscles. Posture isn't a position you choose and then hold — it's an event your brain builds in real time, continuously, and this system can falter at any stage of life, for quite different reasons in childhood and in older age.
Posture isn't a position, it's an event
We tend to treat posture like a photograph: a correct position someone "adopts" and then "holds" through willpower. It isn't. Posture is a dynamic event, recalculated every fraction of a second, adjusting dozens of small muscles to keep the body organised against gravity. No one consciously holds their posture — it's decided behind the scenes, below the level of awareness.
The three pieces of information the brain needs
To build that posture, the brain relies on three sources of information arriving at once: the eyes (where the horizon is, where nearby objects are), the vestibular system in the inner ear (where the head is moving and tilting), and proprioception (the body knowing, without looking, where each part of it sits in space). Human postural control works exactly this way — as a continuous integration of these three sensory inputs (Peterka, 2002).
That trio — vision, vestibular, proprioception — is the same in a six-year-old and in an eighty-year-old. What changes across life is what tends to disorganise those inputs.
In childhood: when infant reflexes stay switched on
In children, a common and under-recognised cause is the persistence of primitive reflexes that should have integrated in the first months of life. Research in pre-school children shows that residual reflex activity is linked to poorer motor performance — the more active the reflex, the lower the score on tests of balance and coordination (Pecuch et al., 2021).
Two examples show how this plays out day to day:
Symmetric Tonic Neck Reflex. Typically active from around 6 to 9 months of age and integrating by roughly 9–11 months, this reflex links head movement to the arms: every time a child lowers their head — to write, for example — the reflex contracts the chest muscles and rolls the shoulders forward, automatically. It isn't a choice. When this reflex stays active beyond the expected window, it's common to see exactly that rounding, shoulders dropping forward when sitting down for a desk task.
Asymmetric Tonic Neck Reflex. Typically active in the first months and integrating by around 6 months, this reflex links head rotation to arm tension: when the head turns to one side, the arm and leg on that side extend while the opposite side flexes. If still active, it's one piece that helps explain the asymmetry no one can quite account for — one shoulder always higher, one side always bearing more weight.
In older age: when the same three inputs lose quality
Decades later, the same sensory trio falters again — not because a reflex refuses to switch off, but because of gradual wear. From roughly 20 to 40 years of age onwards, the vestibular system already begins to lose, slowly and silently, the inner-ear hair cells responsible for detecting head movement. Leg proprioception also loses sensitivity with age, making it harder for the brain to know, without looking, the exact position of the feet and knees (Henry and Baudry, 2019).
To compensate for these two losses, an older person's brain does something understandable but risky: it starts relying much more heavily on vision to balance. That's why older adults tend to lose their balance far more easily in dim light or with their eyes closed — the visual "crutch" that had been compensating for the rest of the system simply isn't available. Add increased co-contraction of the leg muscles and a greater cognitive load just to stand upright, and the result is a slower, less precise postural system, and a fall that becomes considerably more likely (Henry and Baudry, 2019).
Here, unsteady sitting or uncertain walking follows the same logic as the start of this article: it isn't a lack of effort — it's the same three-input architecture, now delivering poorer-quality information, for a completely different reason than in childhood.
Why "posture exercises" alone rarely fix either end of life
Here's why shoulder-blade drills, planks and posture reminders so often don't hold, whether in a child or an older adult: they work at the end of the line, the output — the muscle carrying out the movement. But posture is decided at the start of the system, the input — the information the brain is receiving from the eyes, the inner ear, the body, and, depending on the life stage, from reflexes that shouldn't still be in charge, or from sensors that no longer detect as sharply. Strengthening the output without correcting the input is a bit like turning up the loudspeaker when the problem is in the microphone — the sound gets louder, but it's still distorted.
When the information is well organised, the body organises itself along with it — without anyone having to keep reminding themselves to "sit up straight."
What genuinely helps
- Assessment before correction. Before any exercise, it's worth investigating why posture or balance is disorganised: is it a visual, vestibular or proprioceptive issue, a residual reflex (in childhood), or expected sensory decline (in older age)? Correcting without understanding the cause rarely lasts.
- In childhood: train the system, not the position. Activities that challenge balance, coordination and sensory integration — moving on unstable surfaces, crossing the body's midline, turning the head and trunk independently — help the brain recalibrate its inputs, rather than simply demanding a position.
- In older age: targeted balance and proprioceptive training. Exercises that deliberately challenge balance (single-leg stance, unstable surfaces, supervised eyes-closed practice) help the system keep using — and, to a degree, retraining — proprioception and the vestibular system, rather than relying more and more on vision alone.
- Patience with the process, at either end. Both reflex integration and rehabilitating an ageing sensory system take time. It isn't a one-day fix — it's a process, with assessment and follow-up.
- Seek professional assessment. In children, especially if "poor posture" comes with coordination, handwriting or concentration difficulties. In older adults, especially after any episode of unsteadiness, dizziness or a fall — even a "minor" one.
When to seek help. In children: seek assessment if posture is accompanied by delayed motor milestones, coordination difficulties, reading or writing problems, or persistent asymmetries. In older adults: seek assessment after any fall, episode of dizziness, or growing sense of unsteadiness. Seek prompt medical review for any sudden loss of previously acquired skills, pain, or new neurological symptoms.
Frequently asked questions
Does poor posture always mean weak muscles? Not usually. In most cases the muscle is doing exactly what the sensory information it's receiving is asking of it. The problem is usually the quality of that information — from the eyes, the vestibular system, proprioception, or still-active reflexes — not the strength of the muscle (Peterka, 2002).
Does reminding someone to sit or stand up straight actually work? Rarely, and only briefly. Because posture is built automatically by the brain from sensory information, a verbal reminder doesn't change that information — which is why the position returns as soon as the person's attention moves elsewhere.
Do infant reflexes really stay active in older children? Yes, in some cases. Studies in healthy pre-school children show residual primitive reflexes in a meaningful proportion of children assessed, linked to lower motor performance (Pecuch et al., 2021).
Why do older adults become more unsteady in the dark? Because, with age, the brain comes to rely more heavily on vision to compensate for reduced vestibular and proprioceptive sensitivity. Without enough light, that visual "crutch" disappears and balance noticeably worsens (Henry and Baudry, 2019).
Is there an age beyond which balance training isn't worthwhile? No. The nervous system retains capacity to adapt throughout life. Balance and proprioceptive training remains relevant even at advanced ages, as part of a falls-prevention plan.
How BPR can help
At BPR we assess posture and balance at the root: the sensory systems that feed them, and the factors specific to each person's stage of life — residual reflexes in children, or sensory decline and fall risk in older adults. From there, we build a plan that addresses the cause, not just the symptom. You can book an assessment at bpr.rehab.
References
- Henry, M. and Baudry, S. (2019) 'Age-related changes in leg proprioception: implications for postural control', Journal of Neurophysiology, 122(2), pp. 525–538. doi:10.1152/jn.00067.2019.
- Pecuch, A., Gieysztor, E., Wolańska, E., Telenga, M. and Paprocka-Borowicz, M. (2021) 'Primitive Reflex Activity in Relation to Motor Skills in Healthy Preschool Children', Brain Sciences, 11(8), 967. doi:10.3390/brainsci11080967.
- Peterka, R.J. (2002) 'Sensorimotor integration in human postural control', Journal of Neurophysiology, 88(3), pp. 1097–1118. doi:10.1152/jn.2002.88.3.1097.