Karate changes the brain - and not just through ill-judged kicks to the head.
Brain scans carried out by researchers from Imperial College London and University College London have revealed distinctive features in the brain structure of karate experts, which may be linked to their ability to punch powerfully at close range.
Oddly, previous studies have found that the force generated in a karate punch isn't, as you'd expect, determined by muscular strength, suggesting that it may be governed by the control of muscle movement by the brain.
The study looked for differences in brain structure among 12 karate practitioners with a black belt rank and an average of 13.8 years' karate experience, along with 12 control subjects of similar age who exercised regularly but had no martial arts experience.
The researchers tested how powerfully the subjects could punch, but stuck to short distances - just five centimeters - to make sure the comparison with novices was fair. The subjects wore infrared markers on their arms and torso to capture the speed of their movements.
Unsurprisingly, the karate group punched harder. And 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 was synchronised.
And brain scans showed that the microscopic structure of certain regions of the brain differed between the two groups.
Diffusion tensor imaging (DTI) showed structural differences in the white matter - the bundles of fibres that carry signals from one region to another - of the cerebellum and the primary motor cortex, known to be involved in controlling movement.
The differences in the cerebellum correlated with how well the subjects' wrist and shoulder movements were synchronized when punching, with the age at which their karate experts began training and with their total experience of the discipline.
"The karate black belts were able to repeatedly coordinate their punching action with a level of coordination that novices can't produce," says Dr Ed Roberts of Imperial College.
"We think that ability might be related to fine tuning of neural connections in the cerebellum, allowing them to synchronise their arm and trunk movements very accurately."