The ATNR (asymmetric tonic neck reflex): its role, why its persistence sabotages writing and posture, and how to integrate it (an RNP read).
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Turn your head to one side, and the arm on that side wants to extend on its own. It's the baby's fencing posture, and when it doesn't fade, you pay for it in handwriting, in reading, and on the field.
Hello to you, movement professional,
The asymmetric tonic neck reflex, the ATNR, is one of the best known archaic reflexes, and one of the most telling for anyone interested in writing, posture, or coordination. It's also the one that comes up most often when we talk about retained reflexes in adults and in athletes. We'll look at what it is, which sense it draws on, and what it becomes when it lingers.
The ATNR is an archaic reflex, an automatic motor response triggered by a precise stimulus: head rotation. Turn the baby's head to one side, and you see the famous fencing posture appear: the arm and leg on the face side extend, while the limbs on the opposite side flex. It's automatic, driven by the lower levels of the nervous system, and it can't be willed.
Which sense does it draw on? Its trigger is head rotation, so a proprioceptive input at the neck. But since turning the head also brings the inner ear into play, the vestibular system takes part. The neck triggers, the vestibular system follows, and we keep both: it's this head-neck-balance association that the reflex trains. That leaves the question of what it prepares.
The ATNR appears as early as intrauterine life and acts as a basic template for several skills. By linking head rotation to extension of the arm on the same side, it wires up eye-hand coordination: the baby turns its head toward an object, and its hand goes in the same direction. It also teaches the system to handle the midline, that virtual border down the middle of the body that movement will have to cross in order to, later on, write from left to right or catch with both hands.
Like every archaic reflex, it isn't meant to stay. It normally integrates within the first year, as voluntary control takes over. When it integrates well, it disappears from movement while leaving its gains behind. When it stays, it keeps laying down the law with every turn of the head.
This is where the ATNR gets very concrete. When it stays active, turning the head still triggers a tendency for the arm on the gaze side to extend. For a child bent over a notebook, it's constant sabotage: the moment they turn their head to follow the line, their writing arm is pulled toward extension, the hand tightens, posture at the desk breaks down. Handwriting becomes laborious, tiring, sometimes illegible.
Reading suffers too, because crossing the visual midline becomes costly: the eyes snag, skip words, and the copied work fills with omissions. More broadly, any cross-body coordination, the kind that makes the left and right sides of the body work together, takes extra effort. These signs are valuable indicators, as long as you read them as such and not as a diagnosis rushed into place.
For a long time, retained reflexes were thought to be reserved for struggling children. That's wrong. A study published in 2024 in a sport and performance journal showed that roughly two out of three elite French soccer players kept at least one active primitive reflex, and nearly one in four had an ATNR that wasn't fully integrated. In other words, in high-level athletes, a retained reflex is almost the norm, far from a pathology.
These athletes perform in spite of it, through compensation: they've built strategies to work around the reflex's effect, and it works, but it costs. It's attention and motor availability mobilized nonstop to manage an interference. Which means there's still margin to recover, sitting under the hood. The lens changes completely then: instead of treating a disorder, the work is to free a potential that's been locked away.
Our approach to the ATNR follows from all of the above. We don't try to 'integrate' it with some off-the-shelf exercise repeated blindly. We use it as an indicator: a lingering ATNR points to the input from the head, both cervical and vestibular, and to its coupling with vision. That's the input we rework, through head movement, head-trunk stabilization, and floor work, rather than correcting handwriting or the sporting movement on the surface.
It's the same logic as with proprioception: you read an output of the system, here the residual fencing posture, and you trace back to the sensory input that feeds it. Repeating a disrupted movement won't fix it; recalibrate the input that's disrupting it. Reflex integration then becomes a consequence of the rewiring, never the stated goal.
The asymmetric tonic neck reflex is an archaic reflex: turning the head to one side produces extension of the arm on that side and flexion of the other, the fencing posture. Its trigger is head rotation, an input that's both cervical and vestibular.
It appears as early as intrauterine life and normally integrates within the first year, as voluntary control takes hold. These benchmarks vary from one child to the next, and an assessment by a trained professional is still needed to draw any conclusion.
When the child turns their head to follow the line, the reflex pulls their writing arm toward extension and tightens the hand. Posture at the desk breaks down, handwriting becomes laborious, and crossing the visual midline tires out reading.
Yes, and it's common, including in high-level athletes: a 2024 study found that roughly two out of three elite soccer players kept at least one active primitive reflex, and nearly one in four an ATNR. It's less a disorder than a resource locked up by compensation.
Be wary of miracle cures. The rigorous approach is to read the input the reflex reveals, here the head and its cervico-vestibular and visual coupling, then to recalibrate that input through movement, with integration following as a result.
By the LabO RNP team
The ATNR is one of the most telling reflexes, but you read it alongside the others. See the full grid of archaic reflexes, and learn to recalibrate the head-neck input in RNP training.
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