Amy Van Dyken: Swimmer injured quad-biking

Amy Van Dyken became the first US female athlete to win four gold medals in a single Olympics

A six-time US Olympic gold medal-winning swimmer has severed her spinal cord in a quad-bike accident.

Amy Van Dyken, 41, told emergency responders she could not move her toes after hitting a kerb in Arizona while driving home from dinner.

But her family said Ms Van Dyken awoke from surgery "acting like her typical spunky, boisterous, ebullient self".

In the 1996 Atlanta Games, she became the first US female athlete to win four gold medals in a single Olympics.

She won two additional gold medals in the 2000 Sydney Olympic Games.

'Gasping for air'

Ms Van Dyken was driving home in Arizona from dinner with her husband, former Denver Broncos punter Tom Rouen, when she hit a kerb in the restaurant car park and went over a drop of at least five feet (1.5m).

Mr Rouen told the Denver Post he raced to help her on his own motorcycle and found his wife not breathing.

"I raised up the back of her neck with my hand, she started gasping for air."

Emergency responders said she was found lying on the ground next to the ATV and was then airlifted to hospital.

Van Dyken was a star of the 1996 Games

A letter from the Van Dyken and Rouen families said she had severed her spinal cord at the T11 vertebrae, and that the broken vertebrae came within millimetres of rupturing her aorta.

"Amy awoke within hours of surgery acting like her typical spunky, boisterous, ebullient self and has spent the last 24 hours entertaining her family and her medical staff in the ICU," the letter said.

Mr Rouen told the Post his wife was at the end of a critical period for her recovery and was showing signs of improvement.

But her long-term prognosis is unclear.

In a statement, USA Swimming said they were "devastated to learn of Amy Van Dyken's unfortunate accident this weekend".

"We're happy to hear that she escaped and is now in great care."