Blood vessels play a role in thermoregulation
Hirata Kozo, professor emeritus at Kobe Women’s University, is an expert on body temperature regulation. He says that while the palms make up only five percent of a body’s surface area, they host blood vessel segments called arteriovenous anastomoses (AVA) that play an important role in controlling body temperature. AVA connect arteries and veins.
Hot blood flows into AVA through arteries in the palm. The palm loses heat, and cooled blood returns to the body through veins. Hirata says the heat can dissipate just by exposing hands to air. But touching something cold can bring body temperature down much faster because of the large volume of blood that passes through AVA.
AVA are also located in the bottom of the feet, so cooling them can also be effective.
Packaged ice packs for athletes
Student baseball players at the Kyoto University of Advanced Science are trialing the use of special cool packs that can work for up to two hours. A company in Osaka Prefecture is developing the product to prevent people suffering heatstroke during exercise.
Players cool their palms by holding the packs before they start training. They continue to use them during breaks. Coupled with drinking adequate fluids, it is proving to be an effective strategy.
Coach Kajita Kazuhiro is impressed: "The cool packs are good for lowering the body temperature easily and in a short timeframe. The students can continue exercising well without suffering the effects of heatstroke."
Not too cold
Hirata says items 10 degrees Celsius and below, such as ice, are not recommended for palms as they are too cold. Something around 15 degrees is best.
He explains that overcooling AVA can shrink the vessel segment through which the blood flows, meaning heat is retained.
"Just putting hands and feet in a washbowl filled with cool tap water is enough to reduce the body temperature effectively," Hirata recommends.
Body response not following the heat yet
Hirata says conditions in Japan this summer mean many people are not yet acclimatized to the heat. "June, and the beginning of July, are already scorching, but people’s adaptation to heat – including blood flow and sweat – isn’t at the level for mid-summer. People need to pay attention to that."
"Knowing that our bodies have not yet adapted to the heat, we need to take preventive measures such as using air conditioners and frequent water drinking."