Matt Walls went over the barriers and into the crowd as he tried to avoid a crashHosts: Birmingham Dates: 28 July to 8 AugustCoverage: Watch live on BBC TV with extra streams on BBC iPlayer, Red Button, BBC Sport website and BBC Sport mobile app; Listen on BBC Radio 5 Live and Sports Extra; live text and clips online.England's Matt Walls was involved in a terrible crash in which both he and his bike flew into the crowd at track cycling's Lee Valley VeloPark.
The 24-year-old Olympic champion was treated in the stands for more than half an hour before being taken to hospital for precautionary checks.
Two other riders - the Isle of Man's Matt Bostock and Canada's Derek Gee - were also taken to hospital for tests.
Spectators were also injured, with one taken away in a wheelchair.
The rest of the session was abandoned and spectators were asked to leave while Walls was having treatment.
Walls was "alert and talking", said a Team England spokesperson.
Eight riders in total went down in the crash on the last lap of the men's scratch race qualifying, with medics and coaches rushing to help the cyclists.
Walls had been trying to avoid riders who had fallen in an incident that began on the entrance to a corner. The stricken pair of New Zealander George Jackson and Australia's Josh Duffy were sliding up the banking, forcing Walls up on to the barrier and then over it.
Gee also surfed the top of the barrier but managed to avoid following Walls into the stands. However, he landed heavily and needed medical treatment.
A Birmingham 2022 spokesperson said: "Three cyclists and two spectators have been treated by the on-site medical team.
"The three cyclists have been taken to hospital. The two spectators did not require hospital treatment."
Walls won omnium gold and madison silver for Team GB at last summer's Olympic Games in Tokyo.
