After a Sleepless Night, Who Is Controlling Your Steps?

When metabolism changes, does the same world require the body to organize itself differently?

Attention · Sleep · Motor Control · Biomechanics · Body–Territory · Metanoia

Imagine walking along the same sidewalk on two different mornings. On the first, you slept well. On the second, you stayed awake all night. The obstacles, distance, and route are practically identical. Yet your steps, balance, and the attention required to walk may not be the same.

What changed: motor control, attentional resources, or the physiological condition of the person walking?

A similar question guided Maura Seynaeve, Anna C. Render, Peter C. Fino, and Toon de Beukelaar in their 2026 study, Effects of one night of sleep deprivation on single- and dual-task gait, published in the Journal of the Royal Society Interface. The researchers sought to distinguish the effects of a sleepless night from those produced by walking while performing an additional cognitive task.

1. Walking requires more than moving your legs

Walking depends on continuous adjustments. With every step, the nervous system integrates information about body position, contact with the ground, and balance. Although walking through familiar surroundings may seem automatic, talking, calculating, or focusing on another objective can modify motor control.

In dual-task research, participants perform two activities simultaneously. One possible explanation for changes in walking is competition for limited cognitive resources. Sleep deprivation can also impair vigilance and attention. However, this does not necessarily mean that both challenges operate through the same mechanisms.

If sleep deprivation and dual-task demands affected walking through the same pathways, should their biomechanical effects be similar? This comparison was central to the investigation.

2. The experiment: one night asleep, another awake

The study involved 18 healthy adults, nine women and nine men, with a mean age of 22.2 years. Each participant completed two experimental conditions, separated by approximately one week.

In the control condition, participants slept in the laboratory from 11 p.m. to 7 a.m., with sleep monitored through polysomnography. In the sleep-deprivation condition, they remained awake throughout the night under supervision.

The following morning, participants completed cognitive assessments and walked on a treadmill at a controlled speed. Two walking conditions were evaluated: ordinary walking and walking while performing a 2-back task, which requires comparing successive information with an item presented two positions earlier.

This created four combinations: normal sleep or sleep deprivation, each under single-task or dual-task walking conditions.

The design allowed the researchers to investigate not only whether walking changed, but also how it changed depending on the source of the challenge.

3. What exactly did the researchers measure?

Cameras and body markers enabled three-dimensional reconstruction of foot and pelvis movements. The researchers analyzed step duration, step length, gait variability, foot placement, and indicators of stability.

One important measure was the mediolateral margin of stability, related to body position and control of sideways movement during walking. It is not a direct measurement of fall risk, but it helps identify subtle changes in balance.

The study did not record EEG during walking or directly measure brain metabolism. Its strength lies in the experimental relationship between sleep manipulation, cognitive demands, and biomechanical outcomes.

This distinction matters because scientific measurements should not be interpreted as demonstrating mechanisms they cannot directly reveal.

4. What changed after a sleepless night?

Following sleep deprivation, participants took slightly longer and longer-duration steps on average. The mean mediolateral margin of stability decreased, indicating a measurable change in lateral body control.

Sustained attention was also affected. In a vigilance assessment, median reaction time increased from approximately 388 to 407 milliseconds.

However, accuracy on the 2-back task did not show a statistically significant difference between sleep conditions.

This contrast is important. A sleepless night does not necessarily affect every cognitive function in the same way. Vigilance, working memory, and motor control are not a single, interchangeable capacity.

The results revealed changes in walking and one measure of attention, but not a uniform deterioration across all cognitive tasks.

5. What happened when attention was divided?

When participants walked while performing the 2-back task, they tended to take slightly shorter and quicker steps. Changes also appeared in foot placement and aspects of spatial and temporal gait variability.

However, dual-task walking did not reproduce the same significant decrease in mean mediolateral margin of stability observed after sleep deprivation.

The two challenges produced partially different adaptations.

This is the central finding of Seynaeve and colleagues. It is insufficient to claim that a sleep-deprived person walks differently simply because fewer attentional resources are available.

The results are consistent with the involvement of additional processes, although the study did not directly identify all the underlying mechanisms.

The investigation did not determine which molecular, neural, or metabolic mechanisms caused each difference. Instead, it demonstrated why walking cannot be reduced to competition for cognitive resources alone.

6. The organism does not separate attention from physiology

From BrainLatam's perspective, these findings help us explore the concept of Body–Territory (Corpo-Território).

A person does not first pay attention and then, independently, move their body. Perception, action, alertness, and physiological regulation interact throughout an experience.

Sleep contributes to the organism's recovery and regulation. Sleep deprivation can change the conditions under which movements and decisions occur.

However, the article did not directly measure cellular energy availability, inflammation, or specific metabolic changes. It would be scientifically inaccurate to present such processes as findings of the original researchers.

The demonstrated contribution is more precise: even when the task and experimental environment remain controlled, changing sleep conditions alters measurable aspects of walking.

This provides a concrete foundation for broader questions about the body, experience, and attention.

7. From encounter A to B, and the return to A

We can propose three moments for future investigations.

In A, a person walks after a normal night's sleep.

In B, the same person repeats the task after a sleepless night.

During the return to A, the person walks again after recovering sleep.

Would every biomechanical measure return to its initial pattern? Would attention recover at the same rate as motor parameters? Could the sequence of physiological states influence subsequent responses?

These questions were not answered by the original article.

Testing persistent effects or hysteresis would require monitoring recovery while controlling for practice, fatigue, session order, and individual differences.

Transcranial magnetic stimulation (TMS) could contribute to a separate investigation of cortical excitability across sleep and wakefulness states.

However, TMS is not necessary to explain or recognize the original contribution of this publication.

Here, scientific progress comes from biomechanics and the experimental comparison between sleep deprivation and dual-task demands.

8. The same path, a different encounter

A worker after a night shift, a student who has stayed awake all night, or someone walking while solving a problem may recognize familiar surroundings without responding to them exactly as before.

This does not mean everyone will reproduce the laboratory findings. The sample was small, consisted of young adults, and involved walking on a treadmill.

Nevertheless, the research helps challenge a common oversimplification: familiarity with an activity does not guarantee that it will always be performed in the same way.

The organism's recent physiological history also participates in the encounter.

Metanoia, understood as a hypothesis of transformation through successive experiences, requires more evidence than temporary changes following sleep deprivation.

Still, this study shows why we must investigate not only what someone does, but also the bodily state in which they do it.

In Blog 03, we will move from temporary adaptation to childhood motor development: what can transient bursts of beta activity recorded through EEG reveal about different movement abilities?

Main scientific reference: Seynaeve, M., Render, A. C., Fino, P. C., & de Beukelaar, T. (2026). Effects of one night of sleep deprivation on single- and dual-task gait. Journal of the Royal Society Interface, 23(243), 20260047.

Open data and reproducibility: KU Leuven research data repository.

BRAINLATAM | W47/2026 | BLOG 02/12 — ENGLISH VERSION