Black belts' white matter shows how a powerful punch comes from the brain

Brain scans have revealed distinctive features in the brain structure of karate experts, which could be linked to their ability to punch powerfully from close range. Researchers from Imperial College London and UCL (University College London) found that differences in the structure of white matter - the connections between brain regions - were correlated with how black belts and novices performed in a test of punching ability.

Karate experts are able to generate extremely powerful forces with their punches, but how they do this is not fully understood. Previous studies have found that the force generated in a karate punch is not determined by muscular strength, suggesting that factors related to the control of muscle movement by the brain might be important.

The study, published in the journal Cerebral Cortex, looked for differences in brain structure between 12 karate practitioners with a black belt rank and an average of 13.8 years' karate experience, and 12 control subjects of similar age who exercised regularly but did not have any martial arts experience.

The researchers tested how powerfully the subjects could punch, but to make useful comparisons with the punching of novices they restricted the task to punching from short range - a distance of 5 centimetres. The subjects wore infrared markers on their arms and torso to capture the speed of their movements.

As expected, the karate group punched harder. The power of their punches seemed to be down to timing: the force they generated correlated with how well the movement of their wrists and shoulders were synchronised.

Brain scans showed that the microscopic structure in certain regions of the brain differed between the two groups. Each brain region is composed of grey matter, consisting of the main bodies of nerve cells, and white matter, which is mainly made up of bundles of fibres that carry signals from one region to another. The scans used in this study, called diffusion tensor imaging (DTI), detected structural differences in the white matter of parts of the brain called the cerebellum and the primary motor cortex, which are known to be involved in controlling movement.