A horse must have a certain level of fitness to perform well and endure activity without injury. This is true whether competing at a high level or merely paticipating in occasional trail rides.
The horse's body adapts to the rigors of conditioning with incremental increases in the intensity and duration of exercise through energy-generating processes involved in muscle contraction and development.
Horse muscle energy source
According to research, the immediate source of energy for muscle contraction is adenoisine triphosphate (ATP). Since the concentration of ATP in skeletal muscle is limited, the ATP must be resynthesized if muscle contraction is to continue for more than a second or two. The replenishment of ATP is achieved through anaerobic and aerobic mechanisms in the muscles.
Aerobic metabolism generates energy more efficiently than anaerobic metabolism. As the duration of the exercise bout increases, muscles become more able to utilize aerobic energy. Trotting and slow cantering exercise on level terrain is an example of a primarily aerobic exercise.
Anaerobic energy production occurs with sprint exercises lasting less than 25 seconds. Quarter horse racing and timed rodeo events are examples of exercise that rely principally on anaerobic energy production.
Exercise bouts that involve intermittent burst of activity, such as jumping and cutting involve significant energy production by both aerobic and anaerobic muscle pathways.
The horse's body adapts to training with an adequate period of physical conditioning in the following ways:
- The cardiovascular system improves in the capacity to deliver oxygen to working muscles
- The muscular system improves in the capacity to utilize oxygen and fuel utilization improves
- Bones, tendons, ligaments and muscles increase in size and strength
- The temperature regulating system achieves greater ability to lose body heat during exercise thereby avoiding excessive increases in body temperature
- Neuromuscular coordination improves as the central nervous system adapts to the new skills required for a particular discipline
In other words, as the horse goes through the conditioning processes and becomes more fit, it exercises more efficiently, as well as accomplishing more work before becoming fatigued.
The equine cardiovascular system
Within two to three weeks of the beginning of a regular exercise program, the blood volume increases due to an increase in the number of red blood cells and the volume of plasma. One study showed a 29% increase in plasma volume occurring within 2 weeks of the beginning of low intensity training.
Recovery heart rate
A measure of fitness - relating to how quickly an animal's heart rate drops to normal following a strenuous activity.
This increase in plasma volume along with an increase in red blood cells and hemoglobin provides an increase in the oxygen carrying capacity of the blood.
Over a period of three to six months, an increase in the number of small blood vessels occurs within skeletal muscle. This increases the transit time for blood through the muscle which improves the exchange of oxygen, glucose and fatty acids into the muscle and helps the muscle rid itself of carbon dioxide, lactic acid and heat.
Conditioning also results in enlargement of the heart muscle enabling the heart to circulate blood more efficiently. This results in a reduction in heart rate at a given level of exercise since the heart is able to pump more blood with each beat and doesn't have to work as hard during exercise. This means a fit horse can perform more work before reaching its maximum capacity.
The recovery heart rate is also faster in well-trained horses, particularly endurance athletes. This makes monitoring heart rate during and after exercise an important tool for assessing fitness.
The equine muscular system
A major component of the increase in cardiovascular capacity is an increase in the oxidative capacity of the muscles. The trained muscles are able to produce more energy because they are able to extract more oxygen from the blood.
Aerobic metabolism of glycogen and fat occurs in small structures known as mitochondria located within muscle fibers. Training results in an increase in the size and number of mitochondria within working skeletal muscle.
Low to moderate intensity, long duration training produces the greatest increase in the number of mitochondria and the activity of the aerobic enzymes. These increases occur early in training and allow a more efficient utilization of fuel.
The amount of fat utilized increases allowing limited carbohydrate reserves to be spared. Because depletion of carbohydrate stores may contribute to the onset of fatigues, a greater utilization of fat allows the horse to exercise for a longer period of time before becoming fatigued.
The increased oxidative capacity of trained muscle allows a great proportion of energy to be produced by aerobic pathways early in the exercise period. As a result, production of lactic acid and hydrogen ions is delayed reducing the potential for these by-products to adversely affect the muscle's ability to contract and prolonging the horse's capacity to work at a given intensity.
The supporting structures: bones, ligaments, tendons
Although relatively few studies have been done to examine how the horse's limbs adapt during training, it is known that the supporting structures adapt more slowly to training, taking up to six months before they sufficiently adapt. Recent studies have detected increases in bone density after four to five months of training.
Because of the relatively slow adaptation of supporting structures to the exercise program, an incremental training program that gradually increases the length, speed and repetition of galloping is recommended to increase bone strength since the modeling response of bones is stimulated by fast work.
Recent research has found that the tendons and ligaments of mature horses have a limited ability to respond to training, but younger horses respond more readily.
Although exercise training of horses less than two years old has been thought to be detrimental, the results of recent studies indicate the possibility that early training may enhance development of supporting structures of the limbs and perhaps reduce injury during training and competition. Always keep in mind, however, that a horse of any age should not be pushed beyond its physical limits.
Supporting structures should be monitored closely during training. Each limb should be palpated for signs of swelling, heat and pain on a daily basis, and the training program should be adjusted accordingly.
Thermo regulatory adaptations of the horse
Research shows that the expansion of plasma volume that occurs within the first few weeks of training contributes to improved capacity for thermo regulation so that heat is dissipated and muscles can continue to receive the oxygen and fuels needed to sustain muscle contraction.
Trained horses begin to sweat earlier in the exercise bout than untrained horses showing that fit horses are able to remove excess heat before it overloads the thermo regulatory system.
During warm, humid weather it becomes more difficult for the horse's body to dissipate heat. Horses that are not acclimated to warmer temperatures and high humidity need time to adjust to these conditions if they are to perform optimally.
During the Summer Olympic Games held in Atlanta, Georgia and Sydney Australia, research was conducted to determine the time necessary for horses to acclimate to high heat and humidity. An increase in blood plasma was observed after a week of exercising in hot, humid conditions, with an increase in sweating rate and an earlier onset of sweating taking up to two weeks.
It was determined that a minimum of two weeks is necessary to acclimate a horse to performing in higher heat and humidity without detrimental effects. For these adaptations to take place, the horse must be exercised sufficiently.
Merely exposing the horse to elevated heat and humidity will not cause adaptation to take place. Untrained horse, of course, take much longer to adapt to higher heat and humidity levels. Horses that are forced to continue exercise when dehydrated are in danger of typing up and heat stroke and care needs to be taken to ensure that the horse is never pushed beyond safe limits.
Conditioning has a positive effect on the development of a horse's neuromuscular coordination and enables the horse to complete the skills required for a particular discipline.
Schooling in a particular discipline develops the neuromuscular coordination and mental discipline necessary for participating in individual sporting activities such as dressage, eventing, reining, and cutting.
Neuromuscular coordination development is specific to each competitive sport, and a discussion of schooling techniques relative to the various sports is beyond the scope of this page.
No matter what the activity level of your horse is, whether a highly competitive show horse or a pasture ornament, proper conditioning is a gift you can give your horse to ensure physical and mental health and well-being.