The vacuum doesn’t draw more blood into the hand, it is just enough vacuum to keep the body’s shunting process from occurring - it keeps the capillaries in the palm open and blood circulating through, allowing for heat transfer between the palm and the cooling surface in the glove.
I’ve been looking at this product for years. My question with the pullup improvement is not ‘what is a session’, but the fact that it is basically anecdotal since it was only one of the researchers doing this, not any kind of structured study. It also brings to question how long the increased work capacityu benefit stays with you, ie, I train for 6-8 weks preparing for a deployment, drastically increasing my strength and conditioning workload during that time because the rapid cooling effect of the glove aided me. Now I deploy overseas, and I am working somewhere I don’t have access to power and ice on a regular basis…how long will the training benefit remain when I can no longer use the glove to cool myself as needed?
Where it really shines though, is in core temp reduction. I recall reading info on the website, and one of the studies they actually did do was working groups of people until they were near overheating (sweating, flushed, increased body temp, etc - not necessarily approaching heat exhaustion). One group then went and stood in an air conditioned room at (if I recall) 68 degrees while the other geroup used the glove, and both groups were monitored for changes in core temp. The air con group saw a minor reduction in temp, but it remained elevated for over an hour (again, if I recall - it was a decent amount of time). The glove group saw their temp drop steadily until it leveled out barely above normal. I don’t recall all the parameters, you would have to go look on the site. But that is pretty good heat reduction in my book. And if it really assists in intra-workout recovery, then all the better.
I am actually planning on purchasing one in the near future, for my wife to use (I will obviously use it some as well). My wife has suffered from migraines for approx. 15 years, and one of her triggers is heat. My thought is to get her back in the gym (even CrossFit, it does wonders for the female body;), and use the glove periodically to keep her heat down and stave off migraines.
This brings another question to mind: if your body heat is kept low, what does this do to your metabolism? I won’t claim to know all the ins and outs of the human metabolism, but I wonder if keeping body heat down during exercise might blunt fat burning efforts.