A man used a piece of wood to attack 25-year-old in Benfield Valley by the Portslade and Hangleton boundary.
The attack happened near the West Hove branch of Sainsbury’s as the victim approached the Hangleton Link Road underpass.
The attacker was crouched down holding a large piece of wood that looked like a log.
As the victim came closer the attacker sprang up and repeatedly hit the victim in the body and legs.
The victim fell and kicked out at his attacker, pushing him away before running off past several people near the Hangleton side of the underpass.
He looked round and saw his attacker heading off back up the track to Benfield Way, Portslade.
Sussex Police issued an appeal today for witnesses to the attack which happened just after 9pm on Friday 12 August.
The attacker was described as white, about 21 years old, 5ft 8in tall, slim and with short brown hair.
He was wearing a light grey hooded top and jeans.
A police spokesman said: “Were you one of the people near the underpass?
“Did you witness the assault or do you have information that can assist police in locating the offender?”
Anyone with information is asked to call Brighton CID on 0845 6070999 or the independent charity Crimestoppers anonymously on 0800 555111.