Cardiovascular Fitness - The Foundation for Success

By: Dr John Kohnke BVSc RDA

All jumping and upper level event horses require technical skill and high aerobic exercise capacity developed through specific training. Cardiovascular conditioning is essential to meet the physical needs for speed and stamina, maximum aerobic oxygen uptake for endurance, with minimal accumulation of lactic acid from a too early shift to anaerobic metabolism during the cross country phase. Training to condition for high oxygen uptake, or VO2max, as a measure of aerobic capacity, will ensure adequate fitness for the dressage and show jumping phases, complemented by rhythm, agility and precise movement and skills required for successful overall competition. However, the cross country phase adds an extra dimension of endurance or stamina, as well as efficient recovery within a set time. Cardiovascular fitness is the foundation for all event horses.

Many horses, although adequately conditioned and fit for all phases, may have added physical demands and energy sapping conditions related to the weather, terrain of the cross-country course, often with changing course conditions and challenges of hills, surface variations and jump type on the day. Temperature and humidity can have a large impact during the cross country phase. Riders need to manage the speed and effort expended to avoid dehydration, over-heating and energy depletion, which can all lead to fatigue and exhaustion.

In common with most initial groundwork training, a strong foundation of Long Slow Distance (or LSD) exercise is essential to condition and adapt the muscle and skeletal system to withstand the loading forces imposed by jumping and high speed galloping. In many cases, the LSD training program is carried out over a minimum of 6 months in young horses, but many riders give a young horse up to 12 months of LSD training to help ensure optimum musculoskeletal soundness, cardio development and respiratory adaptation.

A good foundation of LSD conditioning, not only strengthens a horse for more intense and faster challenges during advanced training and competition, but also shortens the time required to re-condition a horse after a lay-off following an intense competition schedule.

Careful and programmed LSD conditioning helps ensure optimum soundness and stamina for competition, but can also limit the degree of physical stress which can result in ongoing soundness issues. Every horse has a risk of accidental mishaps, especially over cross country fences and water jumps, resulting in muscle, ligament or bone injury, which may force downtime at a critical stage of training. Respiratory conditions, especially lung bleeding in upper level horses, can set a horse back 3-6 months to ensure the optimum opportunity and timescale for recovery, combined with specialised nutrition and drug therapy to hasten recovery.

Talking Performance Issue 5 2015 Cardiovascular fitness has an important influence on overall metabolic fitness related to the delivery of oxygen to rapidly contracting muscles. This is also influenced by nutrition to maintain normal red and white blood cell numbers, metabolic function with co-nutrients, parasite control and the overall health of the individual horse. Adaptation to training can also be evaluated by heart rate response to exercise speed and heart rate recovery as a measure of cardiovascular efficiency and fitness for strenuous exercise.

Heart rate recovery can be influenced not only by cardiovascular fitness, but also by the efficiency of heat loss, the effects of dehydration and the efficiency of system re-oxygenation during recovery. The individual horse’s nervous disposition and other environmental influences, such as wind movement, interaction with other horses or animals and ambient temperature and humidity under which the heart rate recovery is being monitored, can influence its use as a measure of fitness. These can all affect the resting heart rate and speed of heart rate recovery after near maximal exercise effort.

The heart rate at a given speed does not change significantly as fitness increases in response to training, although aerobic phase heart rates can decrease as oxygen uptake efficiency is increased with training. The ‘anaerobic threshold’ in an exercising horse is increased towards 170-180 beats/minute with training. Muscles performing above the ‘anaerobic threshold’ use increasing amounts of blood glucose, muscle glycogen and muscle protein, with reduced oxidation of fats, as energy sources under conditions of ‘oxygen debt’. Muscle lactic acid production due to rapid anaerobic energy depletion and the accumulation of high blood lactate, can limit performance and hasten the onset of fatigue.

The maximal heart rate is between 200-250 beats/minute, peaking at a full all-out galloping speed of 16-18 metres/second for most fit, upper level eventing horses. It does not lower with increasing fitness, but if it reaches the highest limit early before maximal exercise demand (as measured by a heart rate meter), it may indicate cardiovascular disease, low red cell parameters (anaemia), airway abnormalities with reduced oxygen uptake, stress or excess fatigue.

(photo: Tazzie Eggins Photography)

Read more including details on Heart Rate Recovery and Handy Hints at http://www.kohnkesown.com/performance5.pdf

Thank you to Dr John Kohnke for sharing this article with us.

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