Horses are able to adapt to a wide range of environmental conditions and can happily live in climates where temperatures fall as low as -40°c or rise as high as +40°c. Due to their size, horses have a small surface area to body weight ratio meaning they retain heat easily which is an advantage in cold climates. In contrast, humans, being smaller, have a greater ratio of surface area to body weight meaning we lose heat more easily than the horse. This explains why there is sometimes a disconnect between how cold we think it is and how cold the horse actually is.

In humans, the effect of a cold environment on exercise performance depends largely on the severity of the temperature and the type of exercise being performed. In fact, being exposed to a moderately cold environment can actually improve performance as the cardiovascular system no longer has to divert blood to the extremities for heat loss. This results in less stress being placed on the heart.

In horses, there is increasing evidence of cold air induced asthma, known as “ski asthma” in human athletes. Cold induced asthma occurs due to narrowing of the airways caused by breathing large volumes of cold, dry air leading to dehydration of the airways.  Normally, cold air isn’t a problem for a healthy horse as they only breathe through the nose, so the inhaled air is warmed and moistened before passing to the lungs. However, studies show that respiratory symptoms in general are very common during physical activity in the cold and the horse’s lungs can be damaged when exercising hard in low temperatures.

Exercise physiologist, Dr David Marlin, suggests temperatures between -5°c and -10°c would be considered cold but there is some evidence that even fit horses strenuously exercising in temperatures of between +4°c and + 5°c can sustain damage to their lungs.

Signs that your horse’s respiratory system may be affected by the cold include:

• Exercise intolerance – not being able to work as hard or for as long as normal
• Increased nasal discharge
• Cough

If your horse shows these symptoms after moderate to hard work, it is likely to indicate airway inflammation. If your horse already suffers from a respiratory complaint, like COPD (chronic obstructive pulmonary disease) or RAO (recurrent airway disease), it’s even more important to stick to activities that don’t require a lot of physical exertion when it’s cold, such as ground work and light hacking.

Other things to consider when exercising in the winter include:

• Warming up
• Cooling down
• Energy intake
• Dehydration
• Injury risk

Warming up

We know that muscles take longer to warm up in cold weather and arthritic joints may ache and need more time to loosen up. To accommodate this and reduce the risk of soft tissue injury, aim to double your warm-up time. If you usually spend 10 minutes in walk before moving onto trot and then 5 minutes of trot before cantering, try upping the walk part to 15-20 minutes and the trot part to 5-10 minutes before you canter.

Cooling off

If your horse tends to sweat when ridden then it’s probably a good idea to give them a clip. Clipping not only helps to reduce the amount the horse sweats but also means they cool off quicker after exercise. A sweaty horse can get quite cold if they have a long coat which takes time to dry. Always ensure your horse is completely cool and dry before rugging and turning out.

Energy intake

Exercising in cold weather uses more energy. Glycogen (stored glucose used for energy) is used up 5 times faster in cold weather and once used up the body starts to convert fat for energy. Great for horses who need to lose weight, but for those who find it harder to keep condition, you’ll need to ensure that they get an adequate number of calories to fuel their work. It’s estimated that for each degree below 0°c the average air temperature falls, the energy intake should be increased by 1%. If not, body weight will drop due to the increased energy required to keep warm, and that’s just at rest. Add in exercise and you can see how quickly a horse in hard work loses condition.

Dehydration

We generally associate dehydration with hot weather but horses can become dehydrated in the winter when water troughs are frozen or water is cold and unpalatable. Ideally aim to keep water buckets warmed to encourage your horse to drink freely and break ice in field troughs at least once a day. Putting a football or similar in the trough can help stop it freezing over and the horse soon learns to bob for a drink!

Injury risk

Another problem common to both hot and cold conditions is the potential for hard, uneven going to result in concussion injuries. On grass or surfaces with ‘give’ in them, the horse’s foot will slide slightly as it impacts the ground which helps dissipate the impact shock reducing concussion. When the surface doesn’t give, the full force of the limb contacting the ground is transmitted up through the foot and leg which can lead to concussion related injuries such as bruising of the foot or strained ligaments / tendons. Aim to limit the amount and intensity of work on ground or arenas that are frozen and where possible wait until later in the day when the surface has thawed.

Exercising in deep snow is great for resistance training and the cold temperature can help reduce inflammation in joints and tendons (it’s also great fun!) but beware hidden ice underneath and the potential for snow to get packed in the feet.

Whilst I’m not a big fan of the winter – especially the long, dark evenings – I do find it a good excuse to get out my books, recharge in front of the telly and perhaps search out a few online courses or webinars in preparation for the spring! Happy days!

The author of this article, Alison Lincoln, holds an Equine Science Degree and has taught on higher education courses in colleges across the UK. Her book 'Equine Sports Coaching' was published in 2008 and remains on the BHS recommended reading list for their coaching qualifications.

For more advice and guidance from Alison, visit her website or see her Horsemart Author Page.