TAMPA -- Army Sgt. 1st Class Mike Rodriguez struggled, losing his balance and falling every so often as he worked his way up Africa's highest peak.
But the higher he went up Tanzania's Mount Kilimanjaro, something unexpected happened.
The effects of his traumatic brain injury -- the result of more than 20 years of combat and training as a Green Beret -- seemed to diminish. The often debilitating migraine headaches he suffers at sea level ceased.
"I have a theory that it may be because I was concentrating so hard on breathing to get up the mountain," Rodriguez said.
It is a theory that will be tested 8,000 miles away from Tanzania at the James A. Haley Veterans' Hospital, by Stephen Scott, the chief of the hospital's spinal cord injury center.
The eight-day trek up and down the 19,340-foot summit of Kilimanjaro, aided by the Alaska Mountaineering School, was no tourist trip.
Rodriguez, 38, was taking part in a research mission run by the Combat Wounded Veteran Challenge, a nonprofit organization created by Dave Olson, a retired Navy captain from Palm Harbor.
Rodriguez was on a team of men -- some missing limbs, some suffering from post traumatic stress disorder -- helping researchers on the climb learn more about the effects of altitude and stress on their maladies and prosthetics.
And to prove that losing a limb doesn't mean losing the ability to serve.
It was a difficult journey that had Scott worried about Rodriguez' safety.
"Of course I was concerned," he said. "People who don't have brain injuries are affected by extreme altitude."
Led by Billy Costello, a Green Beret staff sergeant who lost who lost his right leg above the knee to an improvised explosive device in Afghanistan 18 months ago, the team made a final assault on the summit of Mount Kilimanjaro on Jan. 25.
It was late. Snow was falling and so was the temperature -- dropping to about 10 degrees. After an eight-hour climb, the team opted not to spend another four hours walking around to Uhuru Point, only another 360 feet up.
The way up was a tough slog, Costello said.
The altitude and terrain were wreaking havoc on his X-2 prosthetic leg. Instead of walking with a normal gait, Costello, 30, had to lock up the leg and swing it over obstacles.
The elevation was also making it tough to breathe, he said.
"When we were thinking about getting to the top, we were expecting to be up there, singing and dancing and celebrating," said Costello. "But once we got there, we were too worn out. We were just happy to make it, because every step took a deep breath."
Instead of a happy dance, Costello said he sat down, pulled posters out of a rucksack his young children made, and took pictures for them to bring back to their classes at Township 3 Elementary School in Shelby, N.C.
For Costello, reaching the summit was a tremendous success for himself, his team and for wounded troops who want to continue to serve.
Though he is on his way to a medical retirement, Costello said that data he gathered on the trip backs up what he set out to prove -- with the right drive and equipment, those who have lost limbs to war can still carry on the fight without being a battlefield liability.
"It's not just a wish," he said. "We have the concrete data to show it is possible."
The range of extreme conditions found on Kilimanjaro makes the mountain an ideal place to study how prosthetics respond to stress, said Arlene Gilles, program director for the J.E. Hanger College of Orthotics and Prosthetics at St. Petersburg College.
Gilles, whose previous camping experience "was at Disney," said the searing tropical heat at the mountain's base and the numbing cold at the summit allowed her to collect data about how limbs respond to temperature and altitude.
The information she collected, with computer sensing equipment lugged by porters, will be used to help design better prosthetic systems.
In addition to being presented to the Explorers Club, the data will also aid a study she is conducting with St. Petersburg College, Florida State University and the Department of Veterans Affairs to develop adjustable sockets that better fit on the residual limbs.
But perhaps even more impressive than the data -- which she collected by attaching electrodes, hooked up to computers, to the residual limbs of the climbers -- was observing first-hand what the men could endure.
Especially Danny Swank.
A medically retired Army staff sergeant, Swank suffered injuries in Afghanistan nine years ago that forced the amputation of his leg below the right knee and severely damaged his left leg.
Even before embarking on the trip, Swank was concerned that the skin grafts on what was left of his right leg might not hold up. Those concerns came true on Kilimanjaro.
"I felt horrible for him," said Gilles. "Once he started to walk, his skin could not handle the pressure and from the beginning he was in extreme pain because his limb started to break down."
But Swank, she said, "continued to soldier on.
"He was unbelievable," she said. "It was incredible to watch his determination. I kept advising him to stop. He was bleeding, but no way he was going to turn around. He made it to the high camp" at 15,500 feet.
Every morning, before setting off on the mountain, Rodriguez got up and did some agility tests. Then he would go into his tent and, on a Kindle ereader he borrowed from his young son, take a series of aptitude tests on subjects like math and crossword puzzles. He would repeat the process each night after the exhausting climb.
Back in Tampa, Haley hospital's Scott is crunching the numbers.
"What's different about this is that we were not sure how safe it is for people with these types of severe head injuries to go up to these high altitudes," Scott said.
"We weren't sure if the affect on the brain would be positive or negative. My understanding from the preliminary work, is that there was no adverse affect. He could have gone up another 5,000 feet."
The information Rodriguez collects will go a long way toward helping others with head injuries, Scott said.
The traumatic brain injury study will be presented in March at the annual meeting of the Explorers Club in New York, a century-old private organization that helped sponsor the trip.
Scott said he may also seek to publish his findings, which he hopes to complete in a couple of weeks.
"This was an extraordinary accomplishment for these guys," said Olson. "They exceeded their goals and came back with information that will help other combat wounded veterans."