The parents of Devizes motocross rider Jack Davies are keeping vigil at his hospital bedside after he sustained serious injuries in a crash on Sunday.
His sister Amy, 21, said: “We don’t know exactly what happened. Jack is still critical and on a life-support system at the John Radcliffe Hospital in Oxford and we are all, of course, very upset and anxious.
“It is still very early days and the doctors can’t tell us what’s going to happen.”
She said their parents, Lyn and Kevin, are at Jack’s bedside.
Jack, who is 19 and a former pupil at Devizes School, came off his bike during the race at West Kennet Motocross, near Avebury, shortly before 1pm on Sunday, hitting his head.
The Wiltshire Air Ambulance was summoned and Jack was flown to Great Western Hospital in Swindon with serious head injuries.
He was later transferred to the John Radcliffe Hospital.
Miss Davies, who has a twin, Laura, added: “Jack has been interested in motocross most of his life. He really loves doing it.”
The meeting on Sunday was organised by the Devizes Motocross Club, which is affiliated to the Amateur Motor Cycle Association.
Jason Read, one of the organisers of the Devizes Motocross Club, sent his best wishes to Jack for his speedy recovery.
He said: “It was just one of those things. Accidents can happen in any sport. They all come into motocross knowing the kind of things that can happen.
“The club has been going for 30 years and incidents like this are thankfully rare.”
In June last year 18-year-old motocross rider Patrick Stott from Marlborough was flown to hospital after breaking his neck in a crash while taking part in a regional championship meeting in Elvetham, near Basingstoke.
In August last year 14-year-old Jack Hicken, from Longwell Green, Bristol, was airlifted to hospital after a crashing at at meeting at Corsham Scramble Club, breaking his leg and dislocating his hip.
Numerous messages wishing Jack a speedy recovery have been posted on the AMCA Kennet website.