I have POTS/Dysautonomia and live in the Deep South. This vest is truly a game-changer for me in being able to work outside. I am now able to do things I never thought would be possible. It helps keep my heart rate down, and my core absolutely feels comfortable. I took the vest off and my core felt cold to the touch for about a half hour, which was amazing. I got this vest and two spare bladders which I keep frozen in a portable 12V fridge/freezer. This allows me to work for hours outside in the sun. So glad I discovered this product!