Martina Navratilova has spoken of her agonising ordeal which put her in hospital after an attempt to climb Africa's highest peak.
The 54-year-old US tennis legend was carried down Mount Kilimanjaro in a litter in the early hours of Friday after her lungs filled with fluid and she was unable to breathe.
After she was released from hospital in Nairobi, Kenya, where she was treated for high-altitude pulmonary oedema, Navratilova said she knew by Wednesday that she would not be able to reach the summit the 19,340ft mountain in Tanzania.
"I didn't feel badly, I just couldn't breathe. I couldn't get a full breath of air," she said. "Nothing hurt, and for an athlete that's weird. Nothing hurt but I (couldn't) go on."
Navratilova, who battled breast cancer earlier this year, reached nearly 14,800 feet when a doctor with the 27-person climbing team told her she needed to descend.
Quitting, she said, was not in her vocabulary, but "when the doctor said you're going down, you're going down".
She was disappointed and frustrated, but trying to push on would have been dangerous, she said.
The Czech-born winner of 18 Grand Slam singles titles kept a diary during her four-day charity climb.
Navratilova said she had been in great health since mid-August and that her bout with cancer earlier this year had nothing to do with her medical woes.
She was climbing Kilimanjaro to raise money and awareness for the Laureus Sport for Good Foundation. So far she has helped raise £50,000 and noted that failing to reach the top may have generated more publicity than if she had made it to the summit.