Kicking somebody during a fight can be more dangerous than using a sharp or blunt weapon, research shows.
Alcohol is a common cause of fights
A study of 25,000 people admitted to A&E found use of feet was more likely to inflict serious injury than blunt or sharp objects or fists.
However, the Violence Research Group in Cardiff, found weapons caused a greater number of severe injuries.
Prevention of kicking and use of blunt objects should be a priority, the study in Injury Prevention concludes.
In total, the researchers assessed 31,000 injuries inflicted on patients attending the University Hospital Wales A&E between 1999 and 2005.
Men accounted for three quarters of patients who attended for violence-related injury.
Almost two thirds reported being attacked by just one assailant, but one in four said they had been assaulted by three or more people at the same time.
The age at which a person was most likely to sustain a serious injury peaked at 47.
A total of 21.5% of the injuries were inflicted with a weapon - 11% with a sharp object, 10.5% with a blunt object.
More than half the injured had been punched, and only 7% had sustained injuries through being kicked while on the ground.
Overall, significantly more severe injuries were caused by the use of weapons, than by unarmed physical assault.
However, the researchers found that people who had been kicked were most likely to suffer serious injury - even more so than those who had been attacked with a blunt or sharp weapon.
Firearms injuries, which were very rare, were not considered.
Although surprised that sharp objects were less likely to cause severe injury, the researchers, from the University of Cardiff, said they couldn't discriminate between use of knives or other sharp weapons such as broken glass in the study, which may have affected the results.
Study leader Professor Jonathan Shepherd, an oral and maxillofacial surgeon, warned that alcohol was a large contributing factor in the use of kicking in fights as drunk people were more likely to fall over.
"There's an important link with alcohol. Often in fights people are kicked when they fall over and one of the ways to reduce kicking is to reduce severe intoxication because fewer people would fall over.
"It's very important that when there has been a kicking or a weapon has been used that charges are brought and the assailants are brought to book.
"There are also messages about making sure that objects that can be used as weapons such as glasses are collected and cleared away."
However, he pointed out that Cardiff was one of the safest cities in the UK.
Mr Martin Shalley, consultant in A&E at Birmingham Heartlands Hospital and president of the British Association of Emergency Medicine said the study reflected his own experience.
"It is more unusual for people to be hurt by fists, it's much more common that people have severe injuries by kicking.
"Once you are on the floor, you're at great risk."