Overview

The Mexico Olympics of 1968 forced the professional sporting world to acknowledge the advantages conferred by altitude training. Many studies have been conducted within the human field of athletics to demonstrate the effects of altitude training. The benefits of altitude training are now taken for granted with the most recent studies concentrating on identifying the best regime to maximise these benefits.

Today, altitude training is considered an essential part of an elite athlete's training. Without this preparation and especially at Olympic standard, athletes carry a significant disadvantage in terms of unrealised speed, endurance and recovery. Many athletes travel abroad to altitude for their training prior to important competitions but recently simulated altitude training, also known as hypoxic training has emerged as a more convenient method of achieving the same physiological benefits and increased performance.

Within 3 years of the Mexico Olympics, the benefits of altitude training came to the attention of the horse racing industry when in 1971 an outsider, Canonero II, won the Kentucky Derby with ease. The colt was prepared by training at high altitude in Venezuela before competing in the Kentucky Derby. By improving oxygen utilization, trainers have access to a powerful, safe and drug-free technology that substantially enhances performance and does not fall foul of Jockey Club Rules.

More specifically hypoxic training results in increased speed, endurance and stamina, and improved recovery. Elite athletes will expect on average a 3-5% improvement in performance which equates to an improvement of roughly 53 to 88 yards over a mile race. Improvements of up to 40% in time to muscle exhaustion have been recorded in people in controlled studies.

Altitude simulation delivers hypoxic (oxygen-reduced) air to the horse, so simulating the oxygen content of air at altitude, regardless of the training location. It has additional advantages over travelling to altitude beyond the expense of transporting horses to unfamiliar surroundings away from training facilities etc. Recent research has suggested that it is the precise cycling between hypoxic and normoxic air (with normal O2 content) in brief intervals that plays a critical aspect in the regime. This effect is not physically possible at altitude.

It is now taken for granted that hypoxic training delivers performance improvement in speed and stamina and a range of physiological benefits. Leading stables are utilising hypoxic training to achieve all these but have also found that hypoxic training will also help with:

•  Acceleration of pre-season fitness training;

•  Improvements in recovery from intense training sessions, races or competitions;

•  Improved ability to maintain high levels of fitness throughout a competition period;

•  Assistance in the maintenance of cardio-vascular fitness in injured or ailing horses forced to reduce their training intensity through musculo-skeletal injury;

•  Assistance in the final preparation for major sports event, including those held at altitude;

•  Assistance in acclimatizing prior to travelling to altitude, shortening the length of time initially required at altitude before performance levels can be increased.

With the ability to train the cardio-vascular system in hypoxic conditions it is now possible to minimise the risk to valuable horses in training, ensuring that they will be more likely to compete in their target races. Overall horse welfare is therefore improved.

Physiological effects in the horse

The overall aim of hypoxic training is to increase oxygen utilisation by the muscles to delay the switch from aerobic respiration of muscle to the less efficient anaerobic respiration where lactic acid is produced and accumulates in the muscle. There are 3 main stages in oxygen transport to the muscle

•  Extraction of oxygen from the air in the lungs to the blood.

•  Combination of the oxygen with haemaglobin on the red blood cells (RBCs) in the blood to take the oxygen to the working muscles.

•  Uptake of the oxygen by the muscle in readiness for utilisation.

In the past trainers have sought enhance one or more of the above stages in order to gain altitude training advantages in a number of ways. The addition of oxygen to water to try to increase the oxygenation of the blood through the digestive tract to supplement the lungs enhances the first stage. Blood doping enhances the second stage and requires the collection of blood and the concentration of the RBCs in order to allow their replacement just prior to a race in order to increase the oxygen-carrying capacity of the blood. These techniques undoubtedly enhance performance to a small degree but they are limited in their effect by the inability to enhance the 3 rd stage.

Hypoxic training leads to improvements in all 3 stages of oxygen transport. Hypoxia is a challenge to the body because oxygen is required to utilise glucose as the primary source of energy for our cells. Under a state of hypoxia, the body strives to produce the required amounts of energy, with less oxygen available in the lungs to do it. The body therefore finds ways of adapting itself to maximise the available oxygen. Having adapted, if it then encounters normoxic conditions it makes extra oxygen available for energy metabolism and performance.

Exposure to hypoxia stimulates up-regulation of Hypoxia Inducible Factor (HIF-1), which promotes an improvement of the body's oxygen utilisation system at every link in the chain. Initially, pulmonary oxygen absorption is enhanced to allow more oxygen to enter the system. At the same time the kidneys signal for an increase in Erythropoietin Hormone (EPO) which stimulates the production of Red Blood Cells (RBCs). An increase in RBCs (and haemoglobin as a sub-unit of the RBC) provides increased transportation for this extra oxygen throughout the body.

At the next level, certain growth factors (VEGF) trigger increased capillarisation, enabling increased oxygen delivery to tissues, muscles and brain. Finally, hypoxia causes a boost in production and rejuvenation of mitochondria (the body's principle oxygen sink and the location of aerobic energy production) and mitochondrial enzymes, allowing more efficient use of oxygen for energy production and enhanced enzymatic anti-oxidative defence.

Aside from these primary systemic changes, exposure to hypoxia is known to have the following physiological effects:

•  Decreased average Heart Rate and Blood Pressure

•  Increased production & release of Human Growth Hormone

•  Stimulation of fat metabolism

•  Decreased oxidative stress from Free Radicals (Reactive Oxygen Species “ROS”)

Alternating the hypoxic environment with the normoxic one ensures that the body does not acclimatise to the hypoxic environment to the point where the advantages diminish.

The best regime has been identified as living in a moderately reduced oxygen environment for 12 hours a day for 21 days. The benefits of this can be further enhanced using an alternating oxygen environment during a period of very low intensity exercise. This utilises a significantly reduced oxygen environment alternating with a normoxic environment.