Be cautious of 'invisible heat' during indoor summer workouts
2026-07-13
Recently, a heartbreaking news spread through the badminton community: 17-year-old national first-class badminton athlete Xiao XX passed away on July 4 in Guangzhou during a summer closed training camp due to ineffective rescue from heatstroke. The involved club confirmed this news, sounding an alarm for sports enthusiasts in summer.
Many citizens choose to exercise in indoor venues during summer. However, medical experts warn that ignoring environmental temperature control and exercise load may lead to a hidden trap of indoor heatstroke—during summer indoor exercise, one needs to be more vigilant about the invisible “heat.”
Scientific hydration: Don’t wait until thirsty to drink
“There is a type of heatstroke caused by ‘stuffiness.’” Song Yanli, chief physician of the emergency internal medicine department at Tongji Hospital affiliated with Tongji University, reported that every summer, they encounter many patients with indoor heatstroke. “When running outdoors, natural wind helps sweat evaporate and dissipate heat. But in poorly ventilated indoor spaces using treadmills, heat dissipation efficiency drops significantly.” Song explained that research shows during intense exercise, skeletal muscle heat production can reach 15 to 18 times the basal metabolic rate. If heat cannot be dissipated in time, core body temperature can surge from 37℃ to the fatal 42℃ within just 25 minutes.
More hidden is the humidity trap. When relative humidity exceeds 60%, the evaporation rate of sweat begins to decline significantly; once it reaches 75%, evaporative heat dissipation almost stops.
“In indoor air-conditioned stadiums, sweat evaporation speed increases, and the body surface rarely hangs with sweat droplets, seemingly without ‘heavy sweating.’ This dry illusion makes people subconsciously feel they haven’t sweated much and don’t need to replenish water in large quantities. In fact, in such environments, the total sweat loss of the body is not low, and water continues to be lost.” Zhou Jie, orthopedic joint surgery doctor at Pudong New Area People’s Hospital, has treated many typical cases.
A citizen once played badminton in an indoor venue for the entire afternoon on a weekend, only drinking a small amount of mineral water throughout, feeling they hadn’t sweated much. Shortly after leaving, they suddenly felt palpitations, fatigue, dizziness, and pale complexion. After being sent to the hospital, they were diagnosed with dehydration and electrolyte imbalance.
“Simply drinking mineral water can only replenish water, but cannot make up for the sodium, potassium, and other minerals carried away by sweat.” Zhou suggested that for long-term indoor exercise, low-sugar sports drinks should be chosen to balance water and electrolyte replenishment. The water replenishment standard should not be lower than outdoor exercise of the same intensity. One must never judge water drinking needs subjectively based on the amount of sweat on the body surface, nor wait until thirsty to drink. At the same time, do not use ice water, strong tea, or high-sugar drinks as substitutes.
Clothing: Overlooked heat dissipation details
Besides hydration, exercise clothing is another easily overlooked heat dissipation detail. Many people prefer cotton sports clothes in daily life. But in high-intensity indoor exercise, cotton becomes a “gentle trap.”
“Cotton fabrics have extremely strong water absorption. After absorbing sweat, they stay tightly against the skin for a long time and cannot dry quickly, directly hindering human heat dissipation and causing heat to accumulate in the body without being expelled.” Zhou suggested that during exercise, priority should be given to sports clothes made of quick-drying functional fiber fabrics. Such fabrics can quickly conduct sweat, accelerate evaporation, and improve heat dissipation efficiency. “Professional indoor ball players generally equip quick-drying training clothes, and the design focus of their fabric is different from regular outdoor low-intensity exercise equipment, which also provides clear clothing references for ordinary sports enthusiasts.”
Doctors also remind that during summer, human metabolism is vigorous and physical energy is consumed faster. Indoor exercise should avoid following the crowd to overexert and overload.
“Before exercise, sufficient dynamic warm-up must be carried out. After exercise, a relaxation time of more than 5 minutes should be left to gradually reduce exercise intensity. Do not ‘brake suddenly.’” Li Lingfeng, orthopedic doctor at Shanghai Fifth People’s Hospital, mentioned that immediately taking a cold shower or diving into a low-temperature air-conditioned room after heavy sweating is an extremely dangerous behavior. One should first wipe off sweat, change into dry clothes, sit and rest for a while, and leave only after heart rate and body temperature stabilize.
With increased exercise volume, abrasions and slip-and-fall injuries enter a high-incidence stage. Zhou stated that when minor abrasions occur, do not blindly rinse. In fact, after epidermal abrasion, the small amount of blood and tissue fluid exuded can form a natural protective film. Rinsing with water immediately not only easily brings in bacteria to cause infection but also destroys this protective layer, delaying scab formation and healing. Disinfection treatment should be carried out according to the size of the wound.
Edit：WENWEN Responsible editor：LINXUAN
Source：Wenhui Daily
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