Our brains underestimate our wrist’s true flexibility, study finds

Researchers have found that people systematically underestimate how far their wrists can move. This finding suggests that the brain’s internal representation of the body’s movement range is not as accurate as one might assume. The study, published in Communications Psychology, highlights how our brains prioritize safety over precision when estimating the limits of our mobility.

Understanding how we perceive our body’s capabilities is central to motor planning and action control. When we plan movements—whether reaching for a glass or playing a sport—our brain relies on internal models of our body’s mechanics. These models help us estimate how much effort is needed and avoid actions that might cause harm.

While years of experience might lead one to believe we have a precise understanding of our movement limits, research has shown that perceptions of body size, shape, and even weight are often inaccurate. This new study builds on these findings, exploring whether similar biases extend to how we perceive the range of motion of our limbs.

Lead author Artur Pilacinski (@fatresearchcat.bsky.social), a postdoctoral researcher at Ruhr University Bochum, explained the origins of the research. His co-author, Gilles Vannuscorps, had been “studying the cognitive representations of the body’s biomechanical constraints and our ‘motor knowledge’ for a while now, so the idea followed his earlier research interests.” For Pilacinski, the question was less intuitive: “Having a research background in motor planning, I had always assumed that whatever the brain intends to do realistically reflects what the body can actually do, and all errors (e.g., due to fatigue) are adjusted in real time.”

Pilacinski’s own experiences added another layer of curiosity to the study. “It was a bit at odds with my own experiences in rock climbing, where I would miserably fail whenever trying to recreate moves that my more skilled and agile colleagues would do effortlessly,” he said. “So, after we first discussed the idea with Gilles, I started casually asking my friends to estimate how far they think their hands rotate (similar to the movements we tested in the paper) and was surprised their answers were usually far off from their actual movements.”

The researchers conducted two experiments involving a total of 84 participants. In the first experiment, 59 individuals were asked to estimate and then perform the maximum range of wrist rotation in four directions: abduction (away from the body), adduction (toward the body), flexion (bending the wrist forward), and extension (bending it backward). Participants performed these tasks with both their dominant and non-dominant hands.

To ensure accurate measurements, participants’ hands were placed in a specific resting position on a table, aligned with a protractor. For each movement direction, participants first estimated how far they could rotate their wrists by indicating a point on the protractor. Then, they attempted to execute the movement, and their actual range was recorded. Each movement was repeated three times to ensure consistency.

The second experiment focused on motor imagery, involving 25 participants. Instead of performing the movements, participants imagined the maximum range of motion they could achieve and indicated the corresponding position on a protractor. These estimates were then compared to the actual range of motion measured during subsequent physical trials.

The results showed a consistent underestimation of wrist mobility. In both experiments, participants judged their wrists to have a smaller range of motion than they actually demonstrated. This underestimation was more pronounced for the non-dominant hand, which typically engages in fewer precise tasks than the dominant hand. Among the four movement directions, biases were most significant for flexion and extension, while adduction showed the smallest discrepancy.

Interestingly, the results were consistent across both tasks—whether participants physically moved their wrists or simply imagined doing so. This indicates that the bias is not limited to actual movements but extends to the brain’s internal representation of movement possibilities.

The researchers theorized that this underestimation serves an evolutionary purpose. By underestimating their limits, individuals are less likely to attempt movements that might push their joints to unsafe extremes, thereby reducing the risk of strain or injury. While this strategy may lead to some inefficiencies, such as the need for minor corrective movements, it ultimately promotes long-term joint health.

“Your body is more flexible than your brain thinks it is,” Pilacinski told PsyPost. “This bias is to prevent your body from injury in the case the movement goes wrong. As most cognitive biases, this one seems to be actually a feature, reflecting the real world conditions and aimed at maintaining our safety—so it should not be just ignored and converted into a cheesy motivational slogan like ‘you can do more than you think.’”

While the findings were robust, the study has some limitations. For example, the underestimation bias was not consistent across all participants or all movement directions. A few individuals even overestimated their wrist mobility, suggesting variability in how different people perceive their limits. These differences may stem from factors such as motor experience, reliance on visual versus proprioceptive feedback, or individual variations in motor control skills.

“The actual precision of movement estimates relies on the size of the physical movement itself, which might have made our measurements not sensitive enough to precisely estimate smaller movements (like adduction in our study),” Pilacinski said. “This will certainly have to be addressed in our future, follow-up experiments.”

Future research could also investigate how factors like age, physical activity, or training influence these biases. For instance, athletes or individuals undergoing physical rehabilitation might develop more accurate representations of their movement limits through deliberate practice. Understanding how to modify these biases could have practical applications in sports and rehabilitation, where pushing the perceived limits of mobility is often essential.

The study, “Humans underestimate the movement range of their own hands,” was authored by Artur Pilacinski, Antoine Vandenberghe, Gabriella Andrietta, and Gilles Vannuscorps.