
Development of a vest to cool people exercising in hot environments
In recent years, concern about global warming has only increased. Exercise in hot conditions leads to the body’s core temperature rising, leading to an increased risk of heat stroke and lower performance. It is believed that cooling the body in such conditions helps with physical recovery, resists decreases in performance and cognitive functions, and resists increases in the perspiration rate. A variety of methods to cool the body are currently in use - such as ice packs, ice baths, and cryotherapy - but they have significant limitations, such as only being able to cool some parts of the body and issues with transport.
Aiming to create a garment which would effectively cool the body simply by wearing it - and help to prevent subsequent performance loss if worn during rest times – at Mizuno we began development of the “Cold Charge Vest.”
1.The search for effective cooling locations
We chose a vest style, which can be slipped on over sports uniforms, and therefore even worn during competition. Several pockets were provided on the inside, where cold packs can be inserted.
The greatest challenge was how to keep the packs in contact with the body. Cold packs are heavy, and they tend to sag when placed in pockets. On the other hand, the less stretchy the material, the more difficult it is to keep the packs in contact with the body.
To address these challenges, stretchy and non-stretchy fabric was carefully combined in the pockets to fit around the contours of the body, while utilizing stretchy fabric in the underarm area to create a structure which keeps the cold packs in contact with the body as much as possible (Japanese Patent No. 7122892). In addition, we carefully researched the locations which would enable effective cooling with as few cold packs as possible. This research was conducted in collaboration with Professor Hiroshi Hasegawa of Hiroshima University. As a result, pockets for cold packs were located on the neck, the upper back, the underarm, and the chest.



2.Evaluation of cooling effect
The development project then evaluated the difference in performance between wearing and not wearing the Cold Charge Vest. Eight male students performed intermittent exercise (simulating soccer) in hot conditions. Physiological indicators such as core temperature, skin temperature, and heart rate as well as performance were measured, and sensory evaluation was carried out. The results showed that - compared to the students not wearing the vest - the vest group’s heart rates decreased faster after exercise, and their subsequent exercise performance decreased less.
This evaluation was conducted in collaboration with Prof. Hasegawa, and the research results were also published in an international journal. Furthermore, after this research was presented at academic conferences, national teams and sporting organizations both within Japan and overseas have offered to purchase the Cold Charge Vest.

3.Co-creation with partners
Joint development with partners was essential to creating the Cold Charge Vest.
Prof. Hasegawa led many aspects of the project, from the basic research determining cold pack location through to performance evaluation of the completed product. Continuing the collaboration after the Cold Charge Vest project was finished, Prof. Hasegawa created the Mizuno Cooling Body Map, which weights the cooling effect on different parts of the body. The map has also been used in development of products other than the Vest to aid in hot conditions.
Development of the Vest also involved repeated testing and feedback from athletes across multiple disciplines, with the many improvements made ultimately creating a better product.
4. Proven through usage by many elite athletes
After commercial launch in 2021, the Cold Charge Vest was used by many sporting organizations and athletes at the tournament held in Tokyo the same year. Notably, the Japan women's national softball team won the gold medal at that tournament. Pitcher Yukiko Ueno mentioned the contribution of the Cold Charge Vest, which was included in TV programs broadcast during the tournament. In addition, we supplied the Vest to the Japan Institute of Sports Sciences (JISS) after request from the JISS. It is also used by multiple Japanese high school and university soccer teams contracted to Mizuno.
By continuing to develop products such as the Cold Charge Vest which help athletes cope with the changing climate, we aim to assist their performance, supporting sporting activities through offering better sporting goods.