1. How Clothes Change the Way Your Body Loses Heat During Exercise
Think about the schoolyard after a run. Your body feels intensely hot. Clothes affect how heat moves in and out of your skin. The Ministry of the Environment and the Ministry of Education, Culture, Sports, Science and Technology created a guide for schools to prevent heatstroke. It explains that clothing influences this heat exchange [1].
For hot days, light clothing is recommended. The fabric should absorb sweat and allow air to pass through. Hats are used to block direct sunlight [1]. The same guide notes that indoor sports with thick clothes or protective gear are associated with more heatstroke cases. It suggests removing or loosening gear during breaks to let body heat escape [1]. Gym clothes are not protective gear; they are light. But does color matter too?
2. Why Light Mesh Tops and Shorts Are Recommended for Gym Class
Materials from Nara Prefecture on school safety recommend light clothing with good sweat absorption and ventilation. They also suggest colors that do not absorb heat, such as white [2]. The "best" outfit for hot weather is described as a white, mesh-like, quick-drying short-sleeved shirt and shorts [2]. Mesh is fabric with small holes. Note that white is not required; it is a recommendation. This guide covers general activities in the heat, not just school gym rules. So, what about movement and safety?
3. Why Hoods and Strings Are Avoided in Gym Clothes
Physical Education is not just running. It includes bars, mats, and jump ropes. An article supervised by a former elementary school teacher advises avoiding items that could get caught, such as hoods or strings [3]. Hard items like zippers can hurt if you bump into someone. If sleeves are too long and cover your hands, you cannot put your hands out when you fall, which is dangerous [3]. This advice comes from one article supervised by a former teacher. It is not an official school rule, but one explanation. What happens to sweat?
4. Why Some Schools Do Not Allow Undershirts Under Gym Clothes
In 2021, the Yokohama City Board of Education explained their policy of not allowing undershirts under gym clothes. A representative cited concerns about hygiene and the fact that sweat-soaked undershirts may cool the body, according to the representative's view [4]. However, the same representative said that banning undershirts without a clear reason is not desirable. Some schools ask students to bring a change of clothes [4]. This is not a national rule; it is a decision made by each school. So far, we have looked at the body. What about identity?
5. Why Gym Clothes Have Name Tags or Embroidery
Some reports explain that name tags or embroidery on gym clothes help teachers identify students. This is useful when dozens of children wear the same clothes. In June 2024, a proposal to Nagasaki City asked to remove name tags for privacy reasons. The city replied that the use of name tags is decided by each school [5]. The idea of "identification" comes from reports, not the city’s page. Whether it is necessary is left to each school. Why do schools choose different gym clothes?
6. Why Gym Clothing Rules Differ from School to School
In February 2026, Minato Ward in Tokyo answered questions about designated gym clothes. They stated that each school chooses recommended items based on functionality, price, and school characteristics [6]. The ward also instructs schools to consider the burden on parents and ease of purchasing [6]. Different schools and regions may prioritize heat, safety, sweat, or identification differently. Gym clothes are not one perfect solution; they are a combination of purposes chosen by each school. How is your gym uniform designed?
7. How to Check Your Own Gym Clothes for Safety and Comfort
Look at your gym clothes. Do they have strings or hoods? Are there hard zippers? What is the material listed on the tag? Where is the name placed? You cannot know the reason for the rules just by looking at the clothes. You could ask your teacher about the school’s reasons. For heat information, refer to the "Guide for Creating Heatstroke Prevention Guidelines in Schools" by the Ministry of the Environment and the Ministry of Education, Culture, Sports, Science and Technology, specifically the section on clothing [1].