Preparing to compete in the heat

May 27

Background Information

Any athlete who will have to compete in hot conditions will benefit from a period of acclimatisation. However, it is almost impossible to achieve this unless the weather is hot for at least 2 weeks before the target competition. Even if we have a heatwave for several weeks, acclimatisation will not fully compensate for the adverse effects of very hot or hot and humid conditions – but it will almost certainly make a significant difference and should reduce the risk of heat-related illness or injury.

Acclimatising your horse to exercising in the heat


You can only acclimatise a horse to exercising in the heat if:

    • The weather is hot for at least 2 weeks
    • You train during the hottest part of the day.


For this to have any effect, you need to do it often enough – for example:

    • 5–6 sessions/week for 2 weeks will probably be very effective
    • Sessions every other day for 2 weeks will probably be quite effective
    • 1 session/week will be completely ineffective.


Some horses appear to find work more difficult in the first few days of acclimatisation; they may also go off their feed and water.

    • If this isn’t improving by day 7, consult your vet.
    • If there is no medical explanation, you can continue trying to acclimatise them but do it more slowly.
    • If the horse’s heat tolerance still doesn’t improve, you may have to accept that they are unable to exercise in hot weather.


What if the weather isn’t hot for 2 weeks before my target competition?
  • In this situation, you won’t be able to acclimatise your horse in time for the competition.

What if the weather is hot for a couple of days before my target competition?
  • In this situation, you won’t be able to acclimatise your horse in time for the competition.
  • In fact, if you do ride your horse in the hottest part of the day in these few days, you may make things worse on the day of the competition.

What else can I do to help my horse before competing on a hot day?
  • Keep your horse in good condition
    Make sure they are very fit and not at all fat

  • If the weather is hot in the days leading up to the competition, but not for long enough to acclimatise your horse (less than 2 weeks):

    • Provide a cool environment for as much time as possible
    1. Stable them or turn them out – whichever provides the cooler environment
    2. Wet them all over every few hours if they appear to be uncomfortably hot (do not scrape this water off – leave the horse to air dry)
    3. Provide shade whenever possible
    4. If they have to wear a fly rug, make sure it is white – you can also soak the rug before you put it on, and every few hours during the day.
    • Exercise in the cool of the morning or evening.
  • Consider the amount of weight the horse will be asked to carry (rider + tack)
    Reduce this if you can.

  • Consider clipping – but also think about the long-term effect this will have on them in the months that follow

    If, on balance, clipping will be a negative for the horse, consider withdrawing from the competition and don’t exercise them in the heat.

  • Consider changing your entry to compete at a lower level.

  • If your horse has any health conditions such as asthma, heart disease, or PPID (Cushing’s disease), ask your vet whether it is advisable to compete on a hot day.

What about electrolytes?
  • The most important electrolytes are sodium, potassium, chloride, calcium, and magnesium.
    These are lost in sweat, droppings, and urine.
  • Almost every horse’s diet is deficient in electrolytes – particularly sodium.
  • This deficiency is worse in hot weather as the increased amount of sweat produced leads to greater loss of electrolytes.
  • If electrolytes aren’t provided in the correct amounts, your horse may become dehydrated, have muscle problems, and/or show reduced performance.
  • All horses should receive supplementary sodium chloride (ordinary table salt).
    ~25 mL/day is usually enough for a 500 kg horse; ideally, split this between 2 feeds.
  • In addition to the salt, horses in work should receive a complete, balanced electrolyte supplement every day.
    ‘Complete, balanced’ means that it contains sodium, potassium, chloride, calcium, and magnesium in the correct amounts.
    The total amount fed should be dictated by the horse’s work level, how much they sweat, how hot the weather is, and what else they are eating; follow the manufacturer’s recommendations.

  • You should supplement electrolytes on a routine daily basis.

    Don’t feed them only on hot days, just before a competition, or if the horse has worked particularly hard; and don’t suddenly increase the amount fed.

Make sure your team knows how to cool a hot horse

Your entire ‘ground crew’ should understand the importance of rapid cooling and know how to achieve it. Well ahead of the event:

  • Go through the BE rapid cooling advice with your entire team
  • Practice at home so that everybody knows what to do

(It might be kinder to do this with a pretend horse, unless the weather is very warm.)