People can bend their wrists further than they think. This is what researchers at Ruhr-Universität Bochum and the Université catholique de Louvain have discovered. They asked 87 people to estimate how far they could move their hand in different directions. The test subjects systematically stated that the mobility of their wrist was less than it actually was. ‘The brain obviously does not have a precise picture of the limits of mobility,’ summarises neuroscientist Dr Artur Pilacinski from Bochum.

Bochum, November, 04, 2024. He describes the results together with Antoine Vandenberghe, Gabriella Andrietta and Prof. Dr Gilles Vannuscorps in the journal ‘Communications: Psychology’ from 1 November 2024.

People have a distorted body image

‘Previous studies by other groups have already shown that people have a distorted body image,’ explains Pilacinski. ‘For example, they systematically underestimate the weight or size of their hands. We were interested in whether there is a similar bias for body movements.’


The researchers examined wrist movements in four different directions. Some of the test subjects were asked to mentally visualise the various hand movements and indicate the maximum point to which the movement would be possible. They indicated their answer on a protractor. The other participants were shown various positions on the protractor and had to decide for each of them whether or not they could achieve them by bending their wrist. Finally, all participants were asked to measure their actual mobility in the four directions: they had to bend their hand inwards and outwards towards their forearm and tilt their wrist towards their thumb or little finger.


Systematically underestimated

For three of these four hand movements, there was a significant difference between the assumed and actual mobility. The participants underestimated their mobility by an average of at least ten degrees. Only for the movement in the direction of the thumb was there no significant difference. ‘Presumably because the wrist is least flexible in this direction and the difference between assumed and actual mobility was too small to be measurable with our method,’ estimates Artur Pilacinski.

People are therefore unaware of the true limits of their mobility. ‘We can only speculate about the reasons,’ says Pilacinski. ‘The most likely explanation is that this bias protects us from injury because we don’t overshoot the mark. We may have to make small corrections to our movements, but this protects our muscles, tendons and ligaments.’

The scientist sees a potential benefit of this finding in the field of top-class sport or rehabilitation, where people are deliberately pushed to the limits of their mobility. Knowing that the presumed limit is not the real limit could help people to better visualise their own limits of mobility and ultimately achieve better mobility.

Funding

The work was supported by Action de Recherche Concertée of the Université catholique de Louvain and the Bial Foundation (grant 260/22).

Originalpublikation:

Artur Pilacinski, Antoine Vandenberghe, Gabriella Andrietta, Gilles Vannuscorps: Humans Underestimate the Movement Range of Their Own Hands, in: Communications Psychology, 2024, DOI: 10.1038/s44271-024-00153-x, (https://www.nature.com/articles/s44271-024-00153-x)

ImageSource RUB Kramer