While it looks like we aren’t going to have a very big show season this year, I can't think of a better time to talk about the physiological component to your equine athletes performance. For this blog I will walk you through a very condensed version of equine physiology and how it relates to training and performance.
When referring to the equine athletic capacity, we are discussing the physiological changes which occur in order to achieve optimal performance. One of the largest components of achieving optimal performance is our equine athlete’s ability to transport oxygen. The oxygen transport chain is responsible for the delivery of a large volume of oxygen to support the high metabolic rates during exercise. During exercise the body needs oxygen to produce energy through oxidation, this is called aerobic exercise.
So, how does oxygen get delivered through the body at high enough rates to sustain exercise? Well that is all in turn due to the cardiac output, also known as CO. CO refers to the heart rate multiplied by the stroke volume (SV), so essentially how much blood is being pumped out of the heart to the body. While the max heart rate doesn’t vary compared to humans, the increased size of the horse's heart itself allows for an increase in stroke volume (SV), and thus a greater CO. The delivery of oxygen is limited by both the CO and the oxygen carrying capacity of hemoglobin. During exercise there is a 50% increase in hemoglobin concentration, which is what oxygen needs to bind with, in order to be distributed throughout the body. This increase in CO and hemoglobin concentration is the physiological change that occurs to provide enough oxygen, thus energy, to produce those strong muscle contractions in our equine athletes.
Muscle Contraction; from a Metabolic Standpoint
When looking at a muscle contraction, from a metabolic standpoint, oxidation of various substances occurs to produce the energy needed for a contraction. Specifically the oxidation of CHO, fat and some minor protein contributors. While horses have large stores of intramuscular substrates, readily available for use during exercise, specifically glycogen, it is our job as owners to make sure we are providing our athletes with every means necessary to replenish those stores. The relative contribution of CHO, fat and protein to the production of energy differs and is dependent on exercise intensity, training state, muscle composition, diet/feeding state, and exercise duration. Lots of variables to consider here.
Exercise Intensity vs Exercise Duration
Increasing your exercise intensity results in increased energy contribution from CHO oxidation and decreased contribution from fat oxidation. Whereas, the opposite is true with an increase in exercise duration. Where increasing exercise duration results in an increase in fat oxidation and a decreased contribution from CHO oxidation, which is due to a decrease in CHO glycogen stores in the muscles. Therefore, there are physiological differences in energy contribution when considering exercise intensity vs. exercise duration. While both of these require oxygen, our equine athletes can also produce energy for a short period of time without a flow of oxygen, and this is considered anaerobic exercise. While it is possible, ultimately long term energy production requires oxidation and oxygen.
Equine Physiology & Training
Now I know I have dragged on but we are getting to the good part! How does understanding all these things benefit me and my training? Well let me tell you, similar to people there is an effective way to train and an ineffective way to train. For training to be effective there must be some degree of what I like to call pushing the boundary. Training our athletes for a sufficient enough duration and intensity to cause some form of strain on this system, and/or the organism. As trainers we want to just push the boundary enough to cause the physiological system to work just that little bit harder, but we do not want to over work it to the point of overtraining.
Overtraining is the imbalance between training and recovery, exercise and exercise capacity, as well as stress and tolerance. Physiologically overtraining can be characterized as a decrease in performance and a decrease in maximum oxygen consumption. Quite often our athletes will express this imbalance with behavioural changes. These changes can present by a decrease in weight, muscle tremors before/during or after exercise, increased nervousness, sweating etc.
I hope this gives you a better understanding of how our athletes body works endlessly to perform for us and hopefully guides you to look at your training program from a new perspective. There are so many variables to consider and it is our job as horse owners and professionals to listen for those signs and clues to create the most optimal training program for our horses!