Olympic champion swimmer Amy Van Dyken-Rouen sat up in her hospital bed for the first time since severing her spinal cord in an all-terrain vehicle accident.

The six-time gold medallist posted two photos on Instagram on Tuesday, one a selfie of her in bed and another of her sitting up with help from two hospital workers. She wore a back brace and had a couple of scratches on her face.

She was in good condition on Tuesday, but her family asked that no more details be released as she recovers, hospital spokeswoman Alice Giedraitis said.

"Doing great today," Van Dyken-Rouen said in one post. "My room is the most decorated in ICU. Thx for ur thoughts & prayers!"

The 41-year-old swimmer was injured on Friday when she hit a curb while riding an ATV near Show Low and flew off a drop-off of about two metres, according to a police report.

Van Dyken-Rouen told emergency workers on the scene she could not move her toes or feel anything on her legs. She was airlifted to a Scottsdale hospital and had surgery to stabilize her spine.

Her family said the spinal cord severed at the T11 vertebrae, and the broken vertebrae came within millimeters of rupturing her aorta.

At the 1996 Atlanta Games, she became the first U.S. woman to win four gold medals at one Olympics. Four years later at Sydney, she added two more golds before retiring.