Players for the San Francisco 49ers trotted off the field during Sunday's game against the Detroit Lions and grabbed for the requisite towels and Gatorade. A few went for something else on the bench, slipping their hands into a coffee-pot-like contraption that stops cramping and overheating.

The device, called the Glove and invented by two Stanford biologists, is used by the Niners during games and at practice for players' health. But its applications are far broader: from treating stroke and heart attack victims to allowing soldiers to remain in the field longer under intense heat.

It's also a proven athletic performance enhancer - billed as better than steroids without any ill effects.

"We use the Glove primarily for health reasons," said Dan Garza, the 49ers' medical director. "But outside of sports, it has potential for a lot of exciting things. This technology is a much more effective way of cooling the core temperature than what we would typically do - misting, fanning, cold towels, fluids."

The Glove works by cooling the body from inside out, rather than conventional approaches that cool from outside in. The device creates an airtight seal around the wrist, pulls blood into the palm of the hand and cools it before returning it to the heart and to overheated muscles and organs. The palm is the ideal place for rapid cooling because blood flow increases to the hands (and feet and face) as body temperature rises.

"These are natural mammalian radiators," said Dennis Grahn, who invented the device with Stanford colleague Craig Heller.

Grahn and Heller also found that cooling overheated muscles dramatically improved physical performance, allowing athletes to work out harder and longer, and hold on to their gains.

"We learned that you can actually reverse that muscle fatigue in a short amount of time," Heller said. "And if you cool muscles during rest, you get a much greater recovery than if you rested without cooling."

In the early 1990s, Heller and Grahn first began looking at using controlled heat to halt tremors in patients coming out of anesthesia. When they put their device over the hand and arm of a patient at Stanford Medical Center, "The core temperature went up so fast," Grahn said, "we thought our recording equipment had broken." The tremors stopped.

Once the license for their heating technology was sold by Stanford, they shifted their focus to cooling. The two were interested in exploring therapeutic uses of lowering body temperature, particularly for people with cystic fibrosis and multiple sclerosis. They turned to exercise as a way to build up a person's internal heat load and then worked to figure out how to "pull it out through vascular structures," Grahn said.

Their first "aha" moment in cooling came after they talked their assistant Vinh Cao into doing his regular workouts in the lab instead of at the gym. His routine included 100 pull-ups. One day, Grahn and Heller started using an early version of the Glove to cool him for 3 minutes between rounds of pull-ups. They saw that with the cooling, his 11th round of pull-ups was as strong as his first. Within six weeks of training with the cooling breaks, Cao did 180 pull-ups a session. Six weeks later, he went from 180 to 616.

"I'll never forget the number 616," said Heller. "He tripled his capacity in six weeks. We were like, 'Wait a minute, this is crazy!' "

While a set of pull-ups might take less than a minute, it's enough for the temperature of those muscles to rise, Heller said. "We learned that you can reverse that muscle fatigue in a short amount of time. And if you cool muscles during rest, you get a much greater recovery than if you rested without cooling."

Soon, members of the Stanford football team began paying visits to the Grahn and Heller lab. "After a while, we were watching these guys and saying, 'Oh gee, he only did 700 sit-ups today,' " Grahn said. Their findings were published in the American Journal of Applied Physiology, and in 2003, they received a $3 million grant from the Pentagon's science division, DARPA: the Defense Advanced Research Projects Agency.

User friendly

The Glove is now being distributed and redesigned by a company called Avacore Technologies of Ann Arbor, Mich. Grahn and Heller are board members and working with the company to create a more user-friendly version of the coffee pot-shaped model - which they call "klutzy" - to make it look and feel like an actual glove. Avacore is in contract with the military to deliver the new, streamlined gloves by the end of the year. Some 100 units of the cooling device are in Iraq with the 101st Airborne Division.

It is also being used by other football teams, including the Oakland Raiders and the Miami Hurricanes, and by American cyclists who competed in this year's Tour de France.

"The real benefit to humanity from this technology is that we will be able to induce hypothermia and hyperthermia," said Chuck Hixson, Avacore's president. "This is beneficial in medicine because when you have a heart attack or a stroke, if you can lower the core body temperature below 35 degrees Celsius (95 degrees Fahrenheit) in the first hour, you will substantially eliminate the chance of permanent damage of the heart muscle or brain."

The Grahn-Heller lab, tucked away on the Stanford campus, is full of the metal, wire, mesh and neoprene carcases of earlier cooling and heating gadgets. The biologists, who have worked together since 1986, are a bit of an odd couple. Grahn, 58, a former minor-league hockey player, arranges his office into piles, stacks and more piles. He says, "I keep my exercise levels appropriate for my age and general state of decrepitude."

Heller, 65, on the other hand, is upbeat, organized and exceedingly fit. He dipped into the lab's candy jar - using the Glove to work up to 1,000 pushups on his 60th birthday.

Still, the two agree that the development of the Glove has been a "long slog" that is nowhere near over.

"We've put a lot of years into this," Heller said, "and it's a big deal for us. As biologists, we're not into inventions. We're into mainly how biology works. So it doesn't frequently translate into something that's going to market."

Grahn said their real interest remains in understanding temperature management "for potential medical disorders. We just got sidetracked for 10 years."

Grahn allows, though, that use of the Glove by athletes also has real potential.

"Everyone in sports knows that if you stick a syringe full of steroids in a padded area of your body it will make you play better," he said. "Well, we want to say, 'Instead of that, try sticking your hand in the Glove for three minutes and you'll play better.' "

What is the Glove?

The Glove, formally known as Core Control, is available through Avacore Technologies of Ann Arbor, Mich. It retails for $2,500, but is available at select times throughout the year for less than $2,000. The price is expected to come down with the second generation of the Glove, now in development. Information: