Endurance Riding, Part 4, Section 1

Heat and Humidity

By Kristene Smuts

In this article I'll talk about the dangers of humidity; over cooling the horse; tying up and thumps; and riding a stallion.

Heat and Humidity

What's so dangerous about humidity, you might ask. Well, let's look at it in more detail. Remember from the previous articles that exercise generates an extraordinary amount of heat which has to be dissipated through sweat. If your horse can't shed this heat, he's liable to go into "boil" mode, where his internal temperature can rise by 1 deg C per hour. In normal exercise mode and in normal heat, your horse will be able to get rid of this internal heat through sweating.

When the air is dry, your horse's sweat evaporates due to his body having more moisture than the surrounding air, thereby cooling him through evaporative cooling. However, as the humidity - moisture content of the air - increases, so your horse's ability decreases to rid his body of internal heat. Why? Because the air is already moisture laden, the sweat can't evaporate but merely pours out of his skin in rivulets, inhibiting the evaporative effects of normal sweating. This results in your horse not being able to cool himself, more sweat is produced which just keeps pouring out, taking much needed water and electrolytes with it. The body temperature doesn't come down and your horse is in danger of over-heating.

There is a condition called anhidrosis which simply means that your horse has altogether lost his ability to sweat, even in normal, sweat producing circumstances. The sweat glands have gone into overdrive mode and have lost their ability to produce sweat, preventing the horse from cooling himself. When this condition manifests itself, your horse is also in danger of becoming over-heated.

To counteract the fluid losses, your horse should drink, at the very least 4.5 - 5 litres of water, for every hour he exercises. Also, the higher the temperature and humidity becomes, the easier you have to be on your horse - don't push so hard! Here's another little calculation - you never thought you'd do so much maths, did you? Take the temperature in deg Celsius and add the humidity factor. The higher the result, the more your horse should drink and the slower you should ride. Here is a quick reference table :

Degrees FHumidityTotalDegrees CHumidityTotalLevel
10050150335083Mod - Haz

Minor = <120 (deg F); <71 (deg C)
Moderate = 121-150 (deg F); 72-88 (deg C)
Hazardous = 151-180 (deg F); 89-104 (deg C)
Extreme Hazard = > 180 (deg F); > 104 (deg C)

Although the Ride Master attempts to get the humidity factor from the Weather Bureau, this isn't always possible but he will warn against possible high humidity, so use your head and if you're feeling uncomfortable, think how uncomfortable your horse must feel, having only 3 times the skin surface area compared to that of the human with which to dissipate heat but being 9 times or more heavier than the human in addition to carrying your weight and tack!

The very best strategy when you're planning to ride in high humidity, is to acclimatise you and your horse at least 3 weeks prior to the ride by boxing to the venue and staying there. Most of us don't have the luxury of being able to do that, so what else can you do? Instead of thinking that you're going to be clever and always ride very early in the morning or late in the afternoon when it's nice and cool, ride at least once a week in the heat of the day, taking it easy with the speed or exertion... all together now, boys and girls - remember golden rule number one!! If you're at the stage of doing interval training, don't do your sprints at this time, do them during the other rides. Also, when a particularly humid day is forecast, don't loll about the house with a cold drink, take the opportunity to go for a ride. I told you you'd become the strange one!

When at the ride, remember to carry your sponge with you and take every opportunity to sponge your horse down, helping him to evaporate his internal heat. Another strategy some veterans use, is to carry a bottle of water with them, wetting the horse in-between water stops, then filling the bottle again at the next stop.

No cooling strategy at a ride or adequate drinking at every water stop can replace good conditioning beforehand. By conditioning your horse well, you'd have developed his muscles to cope with heat dissipation; his aerobic capacity would have improved; by being fit, his pulse rate would be lower; his capillary beds and blood vessels in the skin would have multiplied.

Always remember - if you expect to compete in particular conditions, train for those conditions. You cannot expect your horse to cope well with unexpected conditions if you haven't conditioned him to them. Of course, this also includes terrain underfoot like mud, stones, etc.

But don't think that more is better when conditioning for heat and humidity. Don't always ride in the middle of the day, thinking that you'll be one up on the rest of the pack. By constantly exposing your horse to high heat and humidity, over time you'll be depleting him of electrolytes and because of the extreme assault on his muscles and cardiovascular system, he'll be worn out and will start losing condition. So once again, be clever and balance everything out.

This naturally leads to the next section ...

Tying Up

Part 4, Section 2