According to this story, Navratilova reached as high as 4511 meters (14,800 ft.) on the 5894 meter (19,340 ft.) mountain before she turned back. Apparently, fluid had begun to collect in her lungs, and she was showing all the classic signs of altitude sickness. On Thursday of last week she abandoned her climb and was assisted down the mountain by porters, who took her to a nearby hospital before she was transferred to another in Nairobi where she spent three days recovering.
Navratilova is considered one of the greatest female athletes of all time and lives at altitude in Aspen, Colorado. But she had never been higher than 12,000 feet before this climb, and we all know that altitude can doe weird things to the body. It seems that that is the case here. No matter how fit and well trained you are, altitude is the great equalizer and can bring anyone down.
Fortunately, Navratilova is recovering just fine, and is on her way home. She's disappointed that she didn't complete the climb, as it was to raise funds for Laureus, but she now has a healthy respect for mountaineering, and Kilimanjaro in general.
Just a basic trek indeed!