That may not sound surprising to anyone who's ever played a sport in summer and stopped to splash some water in his face. The face, after all, includes another glabrous surface of the body, so cooling it with water might help stave off exhaustion. But there are other ways to cool down: An overheated athlete might sit next to a mister or dip her hands into a bucket of water. Other research teams have tried to cool the large muscles of the arms and legs, before or after workouts, to enhance performance. We might expect that any of these approaches would help performance on the field or at the gym.
That's not the same as saying they would all be equally effective. To find out which method of cooling works best, we might like to see the magic glove go head-to-head against some other methodologies—including the splash of water in the face. But much of the work from Grahn and Heller's lab has omitted any such comparisons. One study set the vacuum glove against the use of cooling pads on the thigh, the back and the abdomen, while subjects rode a treadmill. The data showed a modest, relative benefit for the device, in terms of keeping heart rates down—but a cooling pad placed along the upper back seemed to do about as well.
Meanwhile, a pair of studies done in other labs has come up with negative results for the gloves. In 2008, the Air Force Research Laboratory reported the results of a run-and-rest experiment, not unlike the one Grahn and Heller did with the Stanford football team. They compared the AVAcore device to a refrigerated gel pack and found that neither improved performance over a control condition, in which subjects were left to recover on their own. The authors concluded that the Stanford glove was "ineffective at improving performance" and called for a stop to further research on the matter.
Grahn and Heller point out that the Air Force study was so mild in its demands—subjects only had to sprint for 30 seconds at a time—that the benefits of cooling would be invisible. It's true the subjects showed little sign of flagging in the heat. But a group at the University of New Mexico followed up two years later with a more exhaustive task. Subjects wearing body armor and heavy backpacks were made to walk a treadmill in a 108-degree room, with breaks for cooling and rehydration. In this one, the AVAcore glove went up against a standard water bath (used for dipping of the hands) and an Army cooling vest that pumps water around the torso. The glove and water bath proved ineffective; only the vest increased endurance.
But that test might have been too difficult, says Grahn. An earlier study from the Stanford lab had shown that the glove's effects diminish as a workout gets more intense. If the Air Force test was too easy, then the New Mexico test was too hard. Another problem, says Grahn, is that both studies looked at the original AVAcore, which suffered from a poor design. To make it work, subjects must grip a cone inside the glove, which could serve to squeeze the blood right out of their palms. The newer version might perform better, he argues.
In any case, Grahn told me, a few negative results don't amount to very much in science. "Anyone can show that something doesn't work," he says. "That's an easy thing to do." So why don't Grahn and Heller run their own versions of this test and see how their device stacks up against some other forms of cooling? Could it be they'd get the same performance-enhancing effect—better than steroids, totally safe—from dunking someone's hand in a bucket of water? "If you can find the right temperature for the water," says Grahn, "if you can do this, that, and the other thing—then yes, you can make it work. I won't argue with that. … But we're making a very efficient, portable bucket."
After a decade's worth of recycled data and overheated coverage, there's no sign that Grahn and Heller's $3,000 bucket has changed the face of professional sports, nor that it ever will. Sure, magic gloves are nice, but it might be time to splash some water on the hype.