Amateur jockey Major Charlie O'Shea was under sedation in intensive care on Monday after suffering "serious chest injuries" following his fall in the penultimate race at Wincanton on Sunday.
O'Shea, who served with 29 Commando Regiment Royal Artillery and won both the Royal Artillery Gold Cup and the Grand Military Gold Cup at Sandown aboard Rolling Dylan earlier this year, had three rides at the Somerset venue.
Having finished third in two earlier races, he was unseated at the second fence in the New John Dufosee Novices' Hunters' Chase, where he was riding Paudie.
Wincanton officials abandoned racing before the concluding bumper, as O'Shea was treated on the track for some time before being transferred to Bristol Southmead Hospital.
Clerk of the course Daniel Cooper later said O'Shea was conscious when leaving the track and the Injured Jockeys Fund provided a further update on his condition on Monday morning.
A statement read: "Following a fall at Wincanton racecourse on Sunday 10 April, amateur jockey Major Charlie O'Shea received immediate treatment for serious chest injuries from the onsite medical team before being evacuated by helicopter to Bristol Southmead Hospital.
"He is currently under sedation in intensive care and there will be another update when he has been assessed and treated further and more information is available.
"His wife Kate and family are grateful for the care he has received so far," it added.