Palmar cooling is a method for improving performance in workouts and competition through body temperature regulation. Increasing body heat during exertion leads to fatigue in a few ways. Heat causes changes to enzymes in the muscle cell leaving them less able to continue to contract. Heat also sends signals to the brain which decreases motivation to continue working hard. The palms of the hands have a special network of blood vessels in them called arteriovenous anastomoses (AVAs). AVAs create a highly efficient means of manipulating body temperature in that heat can easily be accepted or dumped though the palms of the hands (similar areas are the soles of feet and hairless portions of face).
Research has shown that palmar cooling between sets of exercise can cause significant improvement in the amount of work that can be done (increased reps per sets and increased sets per workout). However, much more research is needed to find which temperature ranges are most effective and which work to rest ratios result in the greatest effect size. Many of the early studies looked at 3 minute rest intervals between sets and compared work output between when palmar cooling was applied during the rest interval vs when it was not. Palmar cooling consistently beats out non-cooling in these types research designs.
To date, no study has used our device as the intervention and we are not aware of studies looking at different rest interval times or looking at what happens when palmar cooling is applied mid workout. We wanted to see what would happen for ourselves and perhaps spur on some more research into the idea of temperature regulation for performance benefits.
We detailed 2 early internal tests that we did comparing the same test protocols on two different days in this earlier published blog article. To summarize we found that palmar cooling improved performance in both testing situation but that there was a larger difference between cooling and non cooling when the rest breaks were 60 seconds compared to 3 minutes. The image below shows the results of the two different tests. The seated row test had 60 second rest intervals and the shoulder press test had 3 minute rest intervals.
For the next round of testing we wanted to see what would happen when palmar cooling is applied to situations, mid workout. We did this in two ways.
First we did a biceps curl test with sets done max reps to failure with 60 seconds rest between. The first few sets were done without palmar cooling and then for the last few sets, palmar cooling was applied during the 60 second rest. The results can be seen in the graphic below. This shows that the application of palmar cooling reversed the gradual fatigue trend as expected and provided a performance boost of 50% more reps and the this boost was continued for all 3 rounds that cooling was applied.
Video evidence of this test:
Next, we wanted to repeat the same testing protocol but we were curious if palmar cooling (upper extremities) would improve mid workout performance of the lower extremities. Again, we did sets to failure with 60 seconds of rest between. Again, the first few sets were done without cooling during the rest breaks and then before the final 3 sets, palmar cooling was applied during the 60 seconds of rest. This time we used the knee extension exercise to test if there would be a lower extremity response to palm cooling. The results can be seen in the graphic below. This shows that the application of palmar cooling reversed the gradual lower extremity fatigue trend and provided a performance boost from 12 reps back up to 19! The next 2 sets remained higher than before the application of cooling as well.
Video evidence of this test:
These four internal testing findings are very positive and demonstrate how effective and powerful palmar cooling can be. They put numbers to how people report they "feel" when using palmar cooing during their workouts and competitions. Our hope is that these finding spur interest in academic settings to continue testing different protocols through peer reviewed research.
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