UltraFit Magazine - Issue 111, Page 18

by Paul Taylor

The Mexico City Olympics of 1968 was the stimulus for the advent of what we now refer to as high altitude or hypoxic training. This was due to the fact that every single endurance event was won by athletes who either lived at high altitude, or had spent a significant amount of time living and training at high altitude prior to the event. It was recognised that there were certain physiological advantages to having trained in a high altitude environment.

For this reason numerous high altitude training centres were built around the world. Unfortunately, the competitive nature of the sports industry and the fear of missing out on competitive advantage have created an air of secrecy and confusion around the exact nature of the improvements that the athletes have experienced. A large number of research studies on the effects of altitude on performance have taken place, but to date there has been no consensus on the benefits of altitude training. However, many coaches and individuals insist that they benefit from time at altitude, sports scientists point out that these camps can increase motivation to train and therefore suggest that traditional ‘Altitude Camps’ should be rebranded ‘Attitude Camps’. In this article, we will examine the adaptations to, and hard science behind, altitude training and discuss the potential ergogenic effects of subtle alterations to the traditional approach.

Physiological adaptations

Firstly, it is important to understand what happens to our physiology when we spend a significant amount of time at altitude. The underlying problem with high altitude (>2000 m) is that the partial pressure (PO2) of oxygen is reduced in proportion to the fall in barometric pressure and this clearly poses a challenge to athletes (note that for pure anaerobic events no adaptation is required, so this discussion is focused on endurance training and competition).

Generally speaking, the higher the altitude the longer it takes to adapt, although different athletes adapt at a different rate. A number of physiologic changes occur to allow for acclimatisation at high altitude. These changes have complex interactions and are cardiovascular, respiratory and metabolic in nature. They can be divided into immediate (which take place over several days) and long term (several weeks to a few months.

Immediate changes:

• Because of reduced PO2, respiratory rate increases in order to get the same amount of oxygen into the lungs. This increases the amount of carbon dioxide that must be cleared in the lungs, which in turn induces respiratory acidosis.
• Heart rate increases, reportedly due to Catecholamine (adrenalin and noradrenalin) increases. Theses catecholamine increases also increase reliance on glycolysis (use of carbohydrate stores for energy production).
• VO2 max decreases significantly with increases in barometric pressure above around 1500 or 1600m.
• Increased blood pressure.
• Significant dehydration, due to a combination of less water content in the air and increased respiration rate.
• Reduced performance in events above 800m (there may be small improvements in anaerobic events due to reduced air resistance).

Acclimatisation is an adaptation response by the body to allow for improved tolerance to altitude changes. Full acclimatisation and the time for this to occur is a controversial area. While some reports with ‘responders’ indicate a 12-14 day period up to an altitude of 2300 m, others note this process may take several months. The long-term changes listed below occur as this acclimatisation process is taking place.

Long-term changes:

• Decrease in maximum cardiac output a decreased resting and submaximal heart rate.
• Increased VO2 max after acclimatisation, due to increased oxygen transport and utilisation.
• Increased number of haemoglobin, hematocrit and red blood cells due to the secretion by the kidneys of the hormone erythropoietin (EPO).
• A chemical change within red blood cells that makes them more efficient at unloading oxygen to the tissues.
• An increase in the number of mitochondria and oxidative enzymes within muscle cells. These last 3 changes all result in an increased oxygen transport and utilisation.

Performance at Altitude

At altitude the air density (and therefore wind resistance) is much lower, so it is natural to think that performance would improve immediately. However, the fact that there no world records for endurance events have occurred at altitude means that something else must have decreased – that something is the human engine. The body’s adaptation to high altitude helps significantly but doesn’t fully compensate for the lack of oxygen, as there is a drop in VO2 max of around 2% for every 300 m elevation above 1500 m (even after allowing for full acclimatisation). Whilst altitude training undoubtedly improves performance at altitude compared with those who have not acclimatised, performance at altitude is reduced compared to performance at sea level.

Performance at Sea Level After Altitude Training

While adaptation to high altitude makes you better at high altitude it hasn’t proved useful for making you faster at sea level. A lot of coaches believe that sea-level performance after altitude training is enhanced, but the scientific evidence now clearly shows that traditional high altitude training may improve performance at high altitudes, but it does not generally enhance performance at sea level (although some individuals may benefit slightly in some scenarios). The reason is that some of the adaptive responses (outlined earlier) at high altitude are actually a hindrance at lower altitude.

Live high, train low

There is a significant amount of more recent evidence to suggest that a ‘live high, train-low’ approach may confer some competitive advantage. In this scenario, training is carried out at low altitude (to push anaerobic threshold and VO2 max) but general living and sleeping is done at high altitude so that the hypoxic stress increases red cell mass. This approach appears to give the athlete the best of both worlds, by maximising the improvements of altitude training, but still allowing the athlete to train harder than they could at altitude. In a practical sense it may be difficult to construct, but the last few years has seen a number of custom-built centres springing up all over the world.

There are two ways to achieve this. The first way is to live and train at sea level, but sleep in a special chamber that mimics high altitude. This has been further developed by the construction of huge climate-controlled living spaces (constructed at normal altitude), that allow athletes to live and sleep inside the simulated altitude indoors, but to go outside and train normally. The other option is to live at high altitudes (such as in Colorado) and train in a special chamber that mimics sea level. Both of these approaches have been shown to improve endurance performance at sea level. In what is often touted as the definitive study (1) of this type of training, 39 competitive runners were split into 3 groups; those who lived at 2500m and trained at 1250m, those who lived and trained at 2500m and those who lived and trained at sea level. For the ‘live-high, train low’ group, performance in a 5000m time trial was an average of 13 seconds quicker than the other 2 groups, VO2 max had increased and their running velocity at VO2 max had also increased. Other studies have shown 1% improvements in elite male and female runners (2), improved running economy in elite runners (3) and even improvements in 400m running time (4).

Conclusion

It is clear that some confusion still exists on the benefits of altitude training for athletic performance. It is well accepted that a period of acclimatisation is critical for performance at altitude but, despite the insistence of many coaches, sports science research is clear that the vast majority of athletes do not improve their performance at sea level after training at high altitude. The relatively recent advent of a ‘live high, train low’ approach certainly seems to be supported by sports science, although the exact mechanisms of improved performance are yet to be fully elucidated and considerable variations in performance gains amongst individuals remain.