Ice slurry could be key to Japan's beach volleyball team beating the heat at 2020 Games

Japan's Olympic beach volleyball team has joined forces with the Japan Institute of Sport Sciences (JISS) to develop ways to combat the heat for players competing on the hot sand under an unforgiving summer sun.

At the beginning of July, at the training facility for the men's beach volleyball team in Kawasaki, Kanagawa Prefecture, the first field trials began of a beverage made from fine ice and liquid dubbed "ice slurry" to be consumed before practice and at other times.

The three athletes who drank 600 to 700 milliliters of the ice slurry complained of brain freeze, but compared to the three athletes who drank regular beverages, all three who drank the slurry did not feel the heat as severely.

"Mobility and toughness is important for team Japan to make up for what we lack physically," said the men's beach volleyball team strength conditioning coach Yuya Igurashi. "Being too hot to move will not lead to victory." The athletes also cited the humid heat of the Japanese summer dampening the abilities of the players representing other nations as a chance for the team to shine at the Tokyo 2020 Olympic Games. The slurry may just be able to give the players another leg up on the competition.

According to Hiroshima University professor Hiroshi Hasegawa, Daisuke Nakamura, a JISS researcher of heat countermeasures and other experts, the ice slurry is effective in lowering the temperature of areas deep within the body, such as the esophagus and rectum. Internal body temperature is usually roughly 1 degree Celsius higher than the average body temperature of around 36 degrees, and when severe outside temperatures rise above 40 degrees, the functions of the body's central nervous system and metabolism fall significantly, and athletes are more susceptible to falling into a state where they can no longer exercise.

The fine ice in the slurry absorbs heat from within the body when it melts into a liquid after being consumed. Liquid helps ice cool a greater surface area and acts as a source of hydration. If athletes drink the ice slurry made from a sports drink, they can also replenish the concentration of electrolytes like sodium as well as sugar.

The effectiveness of the ice slurry was first presented by a researcher at an Australian university around 2010, and quickly spread around the world. According to experiments, if an individual drinks 7.5 grams of the slurry per kilogram of their body weight over a period of 30 minutes, their internal body temperature will fall 0.6 degrees. If an athlete drinks the slurry before a race or during a game to lower their internal body temperature, then it slows down the rise in their internal body temperature due to exercise, and it is reportedly possible to maintain a high level of physical performance for a longer period of time.

The JISS has used a simple ice slurry machine in the field, and is already verifying the results of the slurry in soccer, sailing and other sports. The biggest hurdle is the amount of the slurry that athletes need to drink for it to be effective. For an individual weighing 60 kilograms, they need to drink roughly 450 grams of the ice beverage to lower their internal body temperature by 0.6 degrees, and some athletes cannot finish drinking the entire amount.

However, Hasegawa explained, "Even drinking as little as 2.5 grams per kilogram of weight can lower body temperature. It is not necessary to drink such a large amount to lower body temperature like is needed in the case of regular water."

"I think I can make a substitution (for the slurry) myself," said Yoshiumi Hasegawa, who will be representing Japan in beach volleyball at the 2018 Asian Games in Jakarta, Indonesia, in August. "I'd like to give it a try."

(Japanese original by Ryuichi Arai, Osaka Sports News Department, and Yuta Kobayashi, Sports News Department)