Scientists have worked out how karate athletes pack such a punch - and say it has more to do with their minds than their muscles.
Karate black belts generate massive power in their punches, but how they generate the force has been a mystery. Previous research has shown that it is not because of their strength.
Now brain scans have highlighted microscopic structural changes that could help them to synchronise shoulder and wrist movements to punch harder.
Researchers at Imperial College and University College London say that compared to complete novices, black belts have better developed nerve connections that relay signals between brain regions.
Images published in the journal Cerebral Cortex show - in white - the areas in the cerebellum and primary motor cortex that were enhanced .
Lead researcher Dr Ed Roberts said: "The karate black belts were able to repeatedly coordinate their punching action with a level of coordination that novices can't produce.
"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.
"We're only just beginning to understand the relationship between brain structure and behaviour, but our findings are consistent with earlier research showing that the cerebellum plays a critical role in our ability to produce complex, coordinated movements."