Using a cooling glove or holding cold packs in hands can help lower core temperature and potentially increase endurance.

“they used the device and I'll talk about what you can do at home but a device where they had people hold on to what was essentially a cold tube. Now this is crucial, the tube can't be so cold that it causes vasoconstriction because then the cold won't pass from the tube to the hand and to the core. But if it's the right temperature, it's neither too hot nor too cold, that cool from the cold tube passes into the hand, these so-called palmer regions and then cools the core and in theory by lowering body temperature would allow the person or the athlete to do more work and indeed that's what they saw.”