Youngsters were warned about the free running craze after a teenager was seriously injured.
The adventure sport involves people running and jumping down public stairways, between buildings and across rooftops.
A 15-year-old boy was treated at Basildon Hospital after falling seven foot between two walls in Pitsea Market on Wednesday night.
Dr Donald Law, who leads an emergency care team at Essex Ambulance Headquarters, said: "We are becoming concerned about the number of youngsters trying this new craze.
"This is not the first time we have seen youngsters with nasty injuries who are trying to copy what they see on television.
"What people have to remember is that they are risking serious injuries both now and long term."
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