PLN
On a hot competition day, it's easy to be fooled into thinking a round looks ordinary: the horse jumps, leaves the course sweaty and panting as usual. Yet, those few minutes stress it thermally much more than training at home, and most of it happens after leaving the arena.
At home, you can manage the heat: you move training to the morning, shorten it, or skip it on the hottest day. This isn't an option at competitions. The start time is set by the schedule, transportation and a sun-exposed warm-up ring add to the strain, and then there are the emotions of competing.
Let's start with the most important thing: the horse's well-being always comes before the result, and in truly extreme conditions, the best form of care might be to withdraw from the competition. Below are the key facts: what happens to a horse's body on a hot day, how to plan for a competition, and why cold water and a scraper should be used differently today than in the past.
Table of Contents
- What happens to a horse after it leaves the course on a hot day?
- Four cooling habits that are worth changing
- How to really cool legs after a ride?
- Why does a horse stand over a full bucket and not drink?
- Electrolytes - when to give and what never to do
- When is it no longer just hot, but heatstroke?
- The thermometer lies, and humidity decides.
- Which horses tolerate heat the worst
- Insects at competitions: mask, spray or fly sheet?
- How to approach competing in hot weather wisely - a brief summary
What happens to a horse after it leaves the course on a hot day?
A horse has a lot of muscle and little skin: it excels at generating power but is poor at dissipating the heat produced by that power. A significant portion of this heat doesn't escape during exertion; it remains in the body. The horse doesn't shed it at the gate; it carries it from the arena within itself and only then tries to deal with it. [1]
It mainly copes by evaporating sweat from its coat, which only works if the air can absorb water: on a dry day, it dissipates most of the heat, but on a humid day, it becomes insufficient. The second way is breathing, so rapid breathing is not a cause for concern unless it persists after a few minutes. [2]
Four cooling habits that are worth changing
This is the part where we most strongly depart from what many of us learned in the stable. Four recommendations repeated for years have no research backing, and one directly worsens cooling.
"Don't pour cold water, or the horse will go into shock." This has been tested and not confirmed. Hosing very hot horses with cold water for half an hour lowered their temperature within minutes, without harm to muscles, electrolytes, or hydration. Waiting is riskier than hosing. [3]
"Always scrape off water." Newer data contradicts intuition. Before the Tokyo Olympics, five methods were compared, and the simplest won: continuous hosing with lukewarm tap water, which was better than icy water with scraping. The key is to keep the horse continuously covered with water cooler than its body, as heat then dissipates through conduction. [4]
In practice: hose, don't scrape, and repeat every minute for the first five minutes. The scraper will be useful later for drying the horse. [4]
"Only cool the neck and groin." Selectively targeting large vessels does not provide a documented advantage. Surface area and water quantity are what matter, so hose the entire horse. In severe heat stress, five buckets won't be enough.
"Wait to hose until the horse is walking around." On the contrary. The first few minutes after exercise are the most valuable because the temperature is highest. Walk the horse after starting the cooling, not instead of it.
And one thing that will save you nerves with the thermometer: rectal temperature always lags, so a lack of improvement after a few minutes doesn't mean cooling isn't working. It means you need to continue. [3]
A practical complement to water, though not a substitute for it, is Over Horse Ice Shower, a concentrate for post-exercise baths that refreshes and cares for the coat. However, the heavy lifting is done by the amount of water and ensuring it keeps flowing.
How to really cool legs after a ride?
Limbs are a separate issue. At a gallop, the temperature inside the tendon rises enough that it's worth cooling the legs after exercise and ensuring regeneration. Once the whole horse's temperature starts to drop, attend to the legs: cold water or a bucket with ice for twenty to thirty minutes effectively dissipates heat (just be careful with the skin during prolonged ice contact). In the evening, as part of regeneration, cooling poultices are effective: Kaoglin Horse cooling clay maintains a cool, moist compress overnight, and cooling gel with menthol pleasantly refreshes fetlocks and muscles after a hard day. [5]
Why does a horse stand over a full bucket and not drink?
This is the most common question: the horse has lost several liters of fluid, the bucket is full, but it won't drink. The answer is physiological and worth knowing.
In humans, sweat is diluted; we lose more water than salt, blood thickens, and thirst appears. A horse's sweat is much more concentrated, so the horse loses water and salt together, blood doesn't thicken, and the thirst alarm doesn't activate. A horse can be severely dehydrated and simply not want to drink; it's not stubbornness, but its physiological design. [6]
The scale of losses is impressive: over ten liters of sweat per hour is normal, and in endurance rides, losses can reach dozens of liters. Dehydration begins faster than most people realize. [2, 6]
Electrolytes - when to give and what never to do
After significant sweat loss, water alone does not replenish lost electrolytes and may not be enough for full rehydration. Replenishing water and electrolytes should go hand in hand, especially after prolonged exercise or transport. [8]
The best time is about an hour before exertion or transport, also during longer work, and another dose in the evening. Make the solution deliberately diluted, as horses won't drink concentrated solutions. [8]
For supplementation, we use powdered Over Horse Electro Horse electrolytes with sodium, chlorides, potassium, and magnesium, and for stables competing every weekend, there's a three-kilogram package. If the horse is picky about powder, it's easier to mix Electro Balance liquid electrolytes into the water, and between competitions, the Vita Lick salt lick allows it to regulate salt intake at its own pace.
With concentrated electrolytes, the horse should have free access to water, especially if already dehydrated. The right amount of water helps maintain proper solution osmolality and supports stomach emptying and intestinal absorption. Electrolytes should not replace watering. [8]
This can be turned into an advantage: a horse that has been given electrolytes will drink more water on its own afterwards. The only condition is to accustom it to the taste of the solution beforehand, at home and without pressure, not half an hour before the start. [7, 8]
When is it no longer just hot, but heatstroke?
A normal rectal temperature at rest is 37.5-38.5 degrees Celsius and increases with exercise. Three limits to remember: above 41 degrees requires immediate, aggressive cooling; around 42 is critical; and we cool until it drops below 38 degrees. No improvement after an hour means calling a vet. [9, 10]
Symptoms that do not require a second opinion:
- cessation of sweating despite high body temperature, meaning a horse that "dries out" on a hot day;
- very high heart rate persisting long after exercise;
- rapid, heavy breathing that does not slow down;
- apathy or, conversely: irritability, agitation, accidental kicking;
- uncontrollability, disorientation, unsteady gait, stumbling.
This order is not random; it describes the progression of exertional heat illness: from irritability, through disorientation, to convulsions. A horse that behaves "strangely" is not being naughty; it may be overheated. [10]
And one thing, without which the rest is just a list of numbers: a thermometer must be in the box. "By hand" assessment doesn't work, even for experienced handlers.
The thermometer lies, and humidity decides.
Thirty-three degrees on a dry, windy day will be easier for a horse to handle than twenty-eight degrees with high humidity and no wind, because then sweat has nowhere to evaporate. This is the most common mistake in assessing conditions. [2, 15]
That's why equestrianism uses the WBGT index, which combines temperature, humidity, and sun into a single number. You don't have to calculate it yourself; a meter or app will do it, but remember: the measurement should be taken in direct sunlight, not in the shade of a tent. [11, 12]
WBGT should be treated as a scale of increasing risk, not a single rigid limit for all horses and disciplines. In a study of racehorses, the risk of exertional heat illness was significantly higher at WBGT above 28°C than below 20°C, and classic guidelines for fully acclimatized, fit horses indicated an upper limit of approximately 32.5°C. The higher the WBGT, the greater the need to reduce workload, closely monitor, and — in extreme conditions — withdraw from competition. No result is worth a horse's health. [11, 15]
The thresholds were established for horses accustomed to heat. A horse that has worked in cool conditions all June is in a worse situation at the same temperature. The strongest risk factor is a previous episode of overheating, as such a horse does not return to square one. [11, 15]
Regulations respond to heatwaves: In June 2026, during a heatwave, the PZJ Judges' College temporarily allowed all levels of competitions to start from 6:00 AM. During subsequent heatwaves, it's worth checking current PZJ announcements before traveling, as the schedule may change. [13]
Remember about transport: it's several degrees warmer in a closed trailer, and sweating during transit can reach dozens of liters per hour, so the horse starts its warm-up already stressed. Travel in the morning or evening, open everything, and make stops for watering.
The same applies to warming up. Temperature rises quickly, so on a hot day, it's worth limiting the length and intensity of the warm-up to the bare minimum, adjusting it to the temperature, humidity, condition, and degree of acclimatization of the horse. On such a day, the horse warms up on its own.
Which horses tolerate heat the worst
Not all horses start from the same place. The hardest time is had by horses with anhidrosis, meaning a partial or complete loss of sweating ability, triggered by heat with high humidity, which is typical of a Polish August. A horse that doesn't sweat on a hot day where others are wet shouldn't compete, as it loses its main way of dissipating heat. [9]
Special attention is also required for horses after overheating, young horses, unacclimatized horses, overweight horses, older horses, and those with respiratory, circulatory, and metabolic diseases. For respiratory problems, consider supporting the airways between competitions, as the air above the arena can be hot and dusty, and Over Horse Deep Breath for inhalation works well here. [9, 15]
There's also good news: a horse can be accustomed to heat faster than it seems. For Olympic-class horses, two weeks of normal training in heat were enough to lower temperature and heart rate during exertion. No separate program is needed; just train in the heat. [14]
With two caveats: the first few days are worse, not better, so don't plan a competition then, and with very high humidity, the benefit of acclimatization is minimal, and no amount of training can replace the decision to withdraw the horse.
Insects at competitions: mask, spray or fly sheet?
Insects are a separate topic. A horse that spends all day swatting flies by the trailer enters the course fatigued differently, so it's worth protecting it. On a hot day, a mask and repellent are often better than a full fly sheet: Over Horse HorseFly Roll-On works well for targeted application, and for the whole horse and the team, there's HorseFly Spray in a five-liter canister. A full selection is available in the horse repellents category.
You can find the rest of the post-workout recovery products in the Over Horse collection, and more broadly in horse care.
How to approach competitions wisely on hot days - a brief summary
- First, ask yourself if you should compete at all. In extreme heat, with high WBGT or IMGW warnings, withdrawing the horse can be a responsible decision. Welfare always comes before results.
- Assess conditions with the right tool, not your phone's thermometer. WBGT measured in full sun is important, because humidity can be more dangerous than the heat itself.
- The plan is made the day before, not on site. Transport during cool hours, electrolytes one hour before exercise and always with water, warm-up half shorter, cooling equipment prepared before the ride.
- Cool with water, a lot and non-stop, immediately after leaving the arena. Do not use a scraper during cooling, do not put on a wet rug and do not wait for walking. Water temperature is less important than making sure it keeps flowing. [4]
- Legs only after the body has cooled down: cold water or a bucket of ice, twenty to thirty minutes. In the evening, add cooling clay and menthol gel as part of regeneration. [5]
- Electrolytes always with access to water. Concentrated preparations should not replace drinking; proper rehydration requires replenishing both water and lost electrolytes. [8]
- Know the thresholds and have a thermometer. Forty-one degrees is a signal for aggressive cooling, the goal is below thirty-eight, and no improvement within an hour means calling the vet. [9, 10]
- Two weeks of training in the heat really changes how a horse tolerates heat. But they don't help with high humidity and don't replace the decision to withdraw the horse. [14]
Everything comes down to one rule: on hot days, preparation wins, not reaction. A horse that is rested, hydrated, and cooled in the first few minutes returns home in shape. And when conditions become extreme, the biggest concern is not another bucket of water, but the decision not to compete. Welfare always comes before results.
For electrolytes and regeneration products for a specific horse, we invite you to the Equishop store at ul. Oświęcimska 9 in Ruda Śląska, and the entire selection can also be found in horse supplements in our online store.
Sources and studies
Numbers [1]–[15] in the text refer to the bibliography below. References to scientific publications, PubMed/DOI and the official PZJ statement are provided.
[1] Hodgson D.R., McCutcheon L.J., Byrd S.K. et al. Dissipation of metabolic heat in the horse during exercise. Journal of Applied Physiology. 1993;74(3):1161–1170. DOI: 10.1152/jappl.1993.74.3.1161. PubMed
[2] Hodgson D.R., Davis R.E., McConaghy F.F. Thermoregulation in the horse in response to exercise. British Veterinary Journal. 1994;150(3):219–235. DOI: 10.1016/S0007-1935(05)80003-X. PubMed
[3] Kohn C.W., Hinchcliff K.W., McKeever K.H. Evaluation of washing with cold water to facilitate heat dissipation in horses exercised in hot, humid conditions. American Journal of Veterinary Research. 1999;60(3):299–305. PubMed
[4] Takahashi Y., Ohmura H., Mukai K., Shiose T., Takahashi T. A Comparison of Five Cooling Methods in Hot and Humid Environments in Thoroughbred Horses. Journal of Equine Veterinary Science. 2020;91:103130. DOI: 10.1016/j.jevs.2020.103130. DOI / ScienceDirect
[5] Wilson A.M., Goodship A.E. Exercise-induced hyperthermia as a possible mechanism for tendon degeneration. Journal of Biomechanics. 1994;27(7):899–905. DOI: 10.1016/0021-9290(94)90262-3. DOI
[6] McCutcheon L.J., Geor R.J., Hare M.J., Ecker G.L., Lindinger M.I. Sweating rate and sweat composition during exercise and recovery in ambient heat and humidity. Equine Veterinary Journal Supplement. 1995;(20):153–157. DOI: 10.1111/j.2042-3306.1995.tb05022.x. PubMed
[7] Butudom P., Schott H.C. II, Davis M.W., Kobe C.A., Nielsen B.D., Eberhart S.W. Drinking salt water enhances rehydration in horses dehydrated by frusemide administration and endurance exercise. Equine Veterinary Journal Supplement. 2002;(34):513–518. DOI: 10.1111/j.2042-3306.2002.tb05475.x. PubMed
[8] Lindinger M.I. Oral Electrolyte and Water Supplementation in Horses. Veterinary Sciences. 2022;9(11):626. DOI: 10.3390/vetsci9110626. PubMed / full text
[9] Kang H., Zsoldos R.R., Sole-Guitart A., Narayan E., Cawdell-Smith A.J., Gaughan J.B. Heat stress in horses: a literature review. International Journal of Biometeorology. 2023;67(6):957–973. DOI: 10.1007/s00484-023-02467-7. PubMed / full text
[10] Brownlow M.A., Dart A.J., Jeffcott L.B. Exertional heat illness: a review of the syndrome affecting racing Thoroughbreds in hot and humid climates. Australian Veterinary Journal. 2016;94(7):240–247. DOI: 10.1111/avj.12454. PubMed
[11] Schroter R.C., Marlin D.J. An index of the environmental thermal load imposed on exercising horses and riders by hot weather conditions. Equine Veterinary Journal Supplement. 1995;(20):16–22. DOI: 10.1111/j.2042-3306.1995.tb05003.x. PubMed
[12] Schroter R.C., Marlin D.J., Jeffcott L.B. Use of the Wet Bulb Globe Temperature (WBGT) index to quantify environmental heat loads during three-day-event competitions. Equine Veterinary Journal Supplement. 1996;(22):3–6. DOI: 10.1111/j.2042-3306.1996.tb05025.x. PubMed
[13] Polski Związek Jeździecki. Komunikat KS PZJ – upały. 25 czerwca 2026 r. — czasowe dopuszczenie wcześniejszego rozpoczęcia zawodów wszystkich rang od godziny 6:00. Official PZJ announcement
[14] Munsters C., Siegers E., Sloet van Oldruitenborgh-Oosterbaan M. Effect of a 14-Day Period of Heat Acclimation on Horses Using Heated Indoor Arenas in Preparation for Tokyo Olympic Games. Animals. 2024;14(4):546. DOI: 10.3390/ani14040546. PubMed / full text
[15] Takahashi Y., Takahashi T. Risk factors for exertional heat illness in Thoroughbred racehorses in flat races in Japan (2005–2016). Equine Veterinary Journal. 2020;52(3):364–368. DOI: 10.1111/evj.13179. PubMed
