At height, the nervous system shifts balance control. Sensory input from the feet is “upregulated” (dialled up), postural muscles (muscles that help you stay upright, balanced and stable) stiffen slightly, and movements become more cautious. This is part of normal proprioception – the body’s internal sense of where it is in space.
Unlike vision, which tells you where things are around you, proprioception tells you where you are.
Near a drop, the brain begins to rely more heavily on signals from the feet, effectively turning up their volume. Small shifts in pressure and sway are amplified, and control of movement becomes tighter and more deliberate. This is quite different from vertigo. Vertigo arises from disturbances in the inner ear or its connections, creating a false sensation of movement, often described as spinning.
The feeling at height is not that the world is moving, but that the body is being held more carefully in place.
What’s striking is that this response is not unique to those who notice it. The nervous system makes these adjustments in almost everyone. For most, it remains in the background. For others, it rises into awareness as a peculiar sensation.
Why the feet?
As the body’s primary point of contact with the ground the feet are one of its richest sources of sensory information. The soles contain a dense population of specialised receptors, including Merkel cells, Meissner corpuscles and Pacinian corpuscles, each tuned to different aspects of pressure, stretch and movement.
Merkel cells respond to sustained pressure, giving a continuous readout of how weight is distributed across the foot – whether you are leaning slightly forward, back, or to one side.
Meissner corpuscles are more sensitive to light touch and subtle changes, detecting the small shifts that occur as the body sways.
Pacinian corpuscles, deeper in the tissue, are exquisitely sensitive to vibration and rapid changes in pressure, allowing the nervous system to detect even the smallest disturbances in contact with the ground.
Under ordinary conditions, these receptors work quietly in the background, allowing you to stand, walk and shift your weight without conscious thought. But near an edge with a drop, their importance is suddenly elevated. The margin for error narrows. Small changes in pressure – the subtle sway of the body, the shifting of weight from heel to forefoot – carry greater consequence.
The nervous system responds by increasing the gain on these signals. In effect, it listens more closely to the feet.
That heightened input does not feel the same for everyone. Some people describe a buzzing or tingling in the soles. Others report a sense of heaviness, as though their feet are being drawn more firmly into the ground. Some feel an urge to grip with their toes, or to widen their stance. Others notice a faint unsteadiness, a need to hold still, or a curious reluctance to move forward. Why is it that some people experience this so vividly, while others are unaware?
Part of the answer lies in how we process sensory information. The signals from the feet are being generated in almost everyone standing near an edge, but not all of them reach conscious awareness. The brain continuously filters incoming information, prioritising what seems most relevant.
The signals from the feet are being generated in almost everyone standing near an edge, but not all of them reach conscious awareness. (file image)
Unsplash / Oliver Schwendener
In some people, that filter is more permissive. Subtle changes in pressure, sway and muscle activity are allowed through, registering as a distinct sensation in the soles. In others, the same information is handled automatically, without ever rising to conscious notice.
Attention plays a role too. Once a sensation has been noticed, the brain becomes more likely to detect it again.
There are also differences in sensory sensitivity. Some people are simply better at detecting fine changes in touch and position – a heightened form of proprioception. For them, the shift in balance control near an edge may feel more pronounced.
Context matters as well. Fatigue, stress, or unfamiliar surroundings can all make the system more noticeable. What this means is that the sensation itself is not unusual. What varies is the degree to which it is perceived. The same neurological adjustment is taking place either way – quietly in the background for some, and vividly, almost curiously, present for others.
*Michelle Spear is a professor of anatomy at the University of Bristol.
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