Training in a Gi in August: Heat, Sweat and What to Actually Drink

Istanbul in August does not cool down after dark. A dojo at seven in the evening is often warmer than the street was at four, because a hall full of people training is a hall full of heat sources. Then we put on a karategi: heavy cotton, doubled across the torso, with a belt wrapped several times around the middle.

That last detail is the one nobody thinks about, and it is why summer karate is a different physiological problem from summer running.

How your body actually gets rid of heat

Muscle is an inefficient engine. Most of the energy you spend on a kata or a round of kumite leaves your body as heat rather than movement. You have essentially three routes for shedding it, and in a hot hall two of them are nearly closed.

• Conduction and radiation move heat into cooler surroundings. When the room is close to skin temperature, there is nowhere for the heat to go.
• Convection carries heat away on moving air. In a still hall with the windows shut, very little air is moving.
• Evaporation is what remains. Sweat cools you only at the moment it evaporates from your skin. Sweat that soaks into cloth or drips onto the floor has cost you water and returned almost nothing.

There is the whole problem. A gi is an absorbent barrier sitting on the largest sweating surface you own. The torso keeps producing sweat, the jacket keeps holding it, and the cooling you paid for never arrives. The obi then compresses several layers over the abdomen, which was already the least ventilated part of you.

This is why a student can be visibly soaked and still overheating. Wet is not the same as cooled.

What heat strain looks like in the dojo

Heart rate rises for the same work, because blood is being sent to the skin for cooling as well as to the working muscles. Effort feels heavier than the clock says it should.

Technique then degrades in a recognisable order. Stances rise and shorten. The pulling hand gets lazy. Turns fall apart before punches do, because turning is the part that costs balance and attention. And the last third of a kata collapses while the first third still looks respectable.

If you coach, that pattern is diagnostic. A student whose form falls apart only in the final section on a hot evening is not lazy, and usually not unfit either. They are cooking.

Measure your own sweat rate once

Sweat rates differ enormously between people, and no chart will tell you yours. Measuring it takes a single session.

• Weigh yourself before class, with as little on as possible, after drying off.
• Train normally. Note roughly how much you drink.
• Weigh yourself again straight afterwards, dried off again, same clothing.

The weight you lost is water, not fat. Add back whatever you drank to get your true loss. A rough working rule used across sport is that once you are down around two per cent of body weight, most people begin to feel it in concentration and in the quality of late-session work. For a 60 kg adult that is a little over a kilo.

Do this once in August and once in a cool month. The difference will tell you more about your own summer training than any general advice can.

What to drink, and when

Front-load it. Arriving already slightly short is common in summer, and you cannot catch up mid-session.

• Drink across the day rather than one large glass before class. Pale urine in the afternoon is an unglamorous but decent check.
• Take small amounts often during class rather than a lot at one break. Large volumes at once sit in the stomach and feel awful during kata.
• Replace the rest over the hours afterwards. Thirst switches off before you are actually topped up.

For a normal hour-long class, water is enough. Once a session runs long, or you are in a hall in the middle of a hot afternoon, sodium starts to matter, because sweat carries salt as well as water. That is what the white marks dried onto a dark gi are. You do not need a sports drink for it. Salt in a normal meal, a glass of ayran, a bowl of corba, olives, cheese, or a savoury snack after training all do the job. The combination that leaves people headachy and flat in the evening is drinking large volumes of plain water while eating almost nothing salty.

Your body does adapt

Heat acclimatisation is real and reasonably quick. Over one to two weeks of regular training in the heat, the body starts sweating earlier and more freely, distributes sweat better, and conserves salt more effectively. Plasma volume increases, which supports both cooling and circulation.

The practical implication is that the worst sessions are the first ones. Someone returning to the dojo in mid-August after a month away has lost that adaptation and should expect a rough re-entry. Do not read the first hot session as a verdict on your fitness.

Children are not small adults

Younger children have more surface area for their body mass, produce more heat per kilo when moving, and are markedly worse at noticing they are thirsty. They will also keep going long after an adult would have sat down, because they are enjoying themselves.

In a summer children's class, the adults set the rules: a bottle with the child's name on it, scheduled drink breaks rather than requested ones, and permission to open the jacket between drills. A child who goes quiet, stops joining in, or mentions a headache stops training, sits down, cools off and drinks. That is not softness. Heat illness in children develops faster than most parents expect.

When to stop

Stop training, move somewhere cooler and get help if you or a training partner shows any of these:

• Headache, dizziness or nausea that does not clear on sitting down
• Skin gone pale and clammy, or sweating that has oddly stopped
• Confusion, slurred words, unusual behaviour or stumbling
• Cramps that lock a muscle rather than passing

The last two are not minor. Confusion in a hot environment is a medical emergency, not a sign that somebody needs to try harder.

Take this into your next class

• Weigh in and out of one session this week and learn your own number
• Drink across the afternoon rather than in the last ten minutes
• Add something salty to the meal after evening training
• Open the jacket during breaks and let the skin actually breathe
• Read the final third of your kata for the heat pattern before blaming concentration

Summer training is not something to avoid. It is something to plan for. If you want to see how a class runs in practice, we teach children's karate, adult karate, self-defense and conditioning at Yakacik Spor Kulubu in Kartal, six days a week, and the first class is free. Book a trial at karatekartal.fit/en/register