Environmental Effects

During an athlete's career, numerous things happen which bring changes in his environment. In the early stages, the most common changes involve long, tiring journeys, sometimes combined with a stay for several days in an unfamiliar place. Later in the athlete's career, there are more severe changes to take note of and to prepare for. There are three environmental conditions which an athlete will have to learn how to acclimatise to. These are the altitude, temperature and time change.

Altitude

At altitude, there is reduced air resistance, suggesting an advantage in activities involving speed, i.e. sprints. The force of gravity is lowered, offering an advantage where relative and maximum strength is critical.

Some immediate effects of exposure to altitude are increased breathing rate, heart rate, giddiness, nausea, headache, sleeplessness and a decrease in VO₂ max. The total impact of these adjustments is a reduction in work capacity. For every 300 metres above 1000 metres, VO₂ max decreases by approximately 2.6%.

The long-term effects of continued exposure to altitude include increased erythrocyte volume, increased haemoglobin volume and concentration, increased blood viscosity, increased capillarisation, continued lower V02₂ max, decreased lactic acid tolerance and reduced stroke volume.

For short-term training at altitude, ts various benefits can be offset by other fundamental drawbacks such as poor facilities, strange diet, different surroundings and homesickness. Benefits must be weighed against these limitations, plus those created by the time change and problems in travelling to the training venue.

On return from altitude training, performances at sea level appear to peak between the 19th and 21st day, and then again, performance improves again between 36 days and 48 days.

Data collected from various elite endurance athletes from multiple sports have shown that training at altitudes between 1.8km and 3km improves endurance-based activities at sea level. At these altitudes, it can take an athlete up to three weeks to acclimatize.

High altitude may result in a drop in your VO₂ max. The magnitude of this decline is approx. 5 to 7% per 1000 metres (Bernhard 1978)^[1]. To overcome this effect, a "live high train low" model was developed where athletes slept at an altitude of 2500 metres but trained at sea level (Levine 1991)^[2].

Hazards of altitude training

Due to the reduced oxygen pressure at altitude, athletes cannot maintain high-intensity training; subsequently, their aerobic fitness may slowly decrease. This reduction in fitness may offset any positive physiological adaptations from altitude exposure (Levine 2002)^[3]. Athletes can become 'overtrained' as it is a common mistake to adopt the same training zone based on heart rates or times, time to perform a certain distance and lactate concentration.

Heart rate at rest and during submaximal exercise will increase proportionately to the level of altitude compared to sea level. With acclimatisation, the resting and submaximal heart rates will decrease but will remain higher than sea-level values. In contrast, a decrease or a similar heart rate during maximal exercise in hypoxic conditions is observed. Training at altitude will result in higher levels of lactate concentration; at a specific intensity of exercise, an altitude-induced performance impairment of about 3% has been observed in 1,500m running and of about 8% in 5,000 and 10,000m running compared to sea level. Similarly, impairments of 2-3% for 100m and 6-8% for 400m swimming or longer have been recorded (Can Med Assoc J. 1973)^[4]. What this means is that an athlete's sea-level training standards cannot be used at altitude.

The dryness and the altitude-induced hyperventilation causes an increase in water loss via breathing (up to 1,900ml/day for a man and 850ml/for a woman). Also, altitude-induced hormonal changes and the release of metabolites during the acclimatisation phase can increase urine production by up to 500ml/day. It is important to drink sufficient fluid while at altitude (up to 5 litres per day) and reduce the use of caffeinated drinks, which can act as a mild diuretic.

Recovery from training is longer, and since sleep can also be disturbed, an excellent way to avoid overtraining is to take an afternoon nap. Nutrition is vital as lower oxygen levels mean that the demand for carbohydrate is proportionately higher, and a good iron status is also desirable for the production of red blood cells. A nutrient-rich diet is also recommended to help counter the possibility of illness and infections due to the suppression of the immune system at altitude.

Symptoms such as headache, vomiting, dizziness, physical and mental fatigue, sleep disturbance and digestive disorders can also occur at altitude. They may require the reduction and modification of training or complete cessation of training.

Ultraviolet radiation is significantly higher at altitude and can cause sunburn or snow blindness. Athletes should protect themselves by using ultraviolet sunscreen and sunglasses.

Preparing for a major competition

The top endurance athletes prepare for major championships with altitude training. The general advice is:

plan two sessions of altitude training

1st at nine weeks before the competition and lasting three weeks
2nd lasting two weeks and ending 3-4 days before the competition

supplement your diet with vitamin C and Iron

Hypoxic Tents

Using a hypoxic tent, an athlete can take advantage of the benefits of altitude training while at home. Regardless of the altitude, the air we breathe contains 20.9% oxygen, 78% nitrogen and 1% trace gases. At altitude, the atmospheric pressure is decreased, and while the content of oxygen in the air remains the same, its pressure and concentration are decreased. In a hypoxic tent, the air pressure is not changed, but the oxygen content is at approx. 15% oxygen is similar to an altitude of 2500m.

In his article "Why loitering within tent may be good for your game" Duncan Mackay examines how the use of hypoxic tents can influence athletic performance.

Malloy et al. (2007)^[5] discuss the influence of a hypoxic environment on human physiology and altitude training's impact on athletic performance.

Temperature

The ability to perform vigorous exercise for long periods is limited by hyperthermia (overheating) and loss of water and salt in sweating. Athletes should know the hazards of vigorous exercise in hot, humid conditions and should be able to recognise the early warning symptoms that precede heat injury.

The circulatory system functions first to deliver nutrients to the working tissues and remove the waste products, and secondly to regulate the transfer of heat from active muscles to the body surface.

Because of this added demand on blood flow, body temperature regulation and circulatory capacity are significantly influenced by the environmental temperature and humidity. When performing in warm, humid conditions, the circulation cannot both supply nutrients to muscle and regulate body temperature to the complete satisfaction of the body. As a result, the athlete's performance is impaired, and overheating becomes a severe problem.

Low levels of dehydration can influence performance, and it is reported by Cheugn (2004)^[7] that a loss of 2% body weight (1kg for a 50k athlete) can reduce performance by 10 to 20% (120 seconds 800 metres reduced to 132 to 144 seconds).

Two factors influencing early fatigue and impaired performance in all types of sports are the depletion of the body's carbohydrate levels and fluids. Athletes should consider the use of sports drinks to replace these.

HEAT STROKE is one of the few potentially lethal complications of sport in a healthy individual.

Time

When we travel in an easterly or westerly direction, for every 15 degrees of longitude, a time change of one hour occurs. The general effect of this time change is upset to those time-linked body functions, e.g. sleeping, waking, eating, bowel and bladder functions. The body will gradually adjust, and a minimum of one day stay for a one-hour time change is regarded as a necessity. Air travel affects the body. e.g. digestion upset, swelling feet and dehydration.

Research by Youngstedt (1999)^[6] concluded that studies that assessed athletic performance have produced mixed results, and further research is required to establish if athletic performance is influenced by air travel.

References

BERNHARD, W.N. (1998) Acetazolamide plus low-dose dexamethasone is better than acetazolamide alone to ameliorate symptoms of acute mountain sickness. Aviat Space Environ Med, 69, p. 793-801
LEVINE, B.D. (1991) Living high-training low: The effect of altitude acclimatization/normoxic training in trained runners. Med Sci Sport Exerc, 23 (S25)
LEVINE, B.D. (2002) Intermittent hypoxic training: fact and fancy. High Alt Med Biol, 3, p. 177-193
Can Med Assoc J., 1973, 109 (3), p. 207-209
MALLOY, D.C. et al. (2007) The spirit of sport, morality, and hypoxic tents: logic and authenticity. Applied Physiology, Nutrition, and Metabolism, 32, 2, p. 289-296
YOUNGSTEDT, S. D. and O'CONNOR, P. J. (1999) The influence of air travel on athletic performance. Sports Medicine, 28 (3), p. 197-207
CHEUNG, S. and LEIVERT, G. (2004) Multiple triggers for hyperthermic fatigue and exhaustion. Exerc Sport Sci, Rev32, p. 100–106

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MACKENZIE, B. (1997) Environmental Effects [WWW] Available from: https://www.brianmac.co.uk/environ.htm [Accessed