A palm-cooling device marketed as a way to boost hot-weather running performance is ineffective, according to a study published in the International Journal of Sports Medicine.
The BEX Runner features a cooled gel pack that is held in the palm while running. The manufacturer claims, "This cooling helps lead to a longer workout, tolerance for a heavier workload, a shorter recovery time and an overall better exercise experience."
Ohio State University researchers say they found otherwise. They had 12 runners do two runs to exhaustion in conditions of 86 degrees Fahrenheit and 50% humidity. They did the runs (on separate days) at 75% of VO2 max, which is toward the faster end of steady-state running pace. The researchers measured not only how long the runners could last at that intensity, but also their core temperature and rating of perceived effort.
The results indicated the palm-cooling device didn't work as advertised. "The use of the BEX Runner palm-cooling device during a run in hot conditions did not eliminate or even attenuate the rise in core temperature," the researchers wrote.
In addition, time to exhaustion at 75% of VO2 max was shorter when the runners wore the device (an average of 46 minutes without the device compared to an average of 41 minutes with the device). Counting the warm-up time needed to reach a core temperature of just less than 100 degrees, total exercise time was similar between the two runs.