Altitude training- how hypoxic conditions can aid sporting performance

Hypoxia occurs when there is a decreased amount of oxygen in body tissues and is measured by a PO2 level of below 300mmHg, with severe hypoxia occurring at values less than 200mmHg. Essentially, this refers to when your body has insufficient levels of oxygen and can be very dangerous unless managed with professional advice. However, the biological state of hypoxia has begun to draw attention within the sporting realm through its ability to aid sporting performance, especially endurance training.

At around 2000m, there is around 25% less oxygen entering the body in a normal breath due to the lowered particle pressure (PO2) of oxygen meaning the body has to adapt to this decreased amount of available oxygen, and this adaptation allows for improved efficiency of breathing and positive modifications in the body’s physiology. The most popular form of this training is known as LHTH (live-high-train-high) and is where athletes live and train at altitudes of around 2000m for between 3-4 weeks (Sinex and Chapman, 2015)  However, alternate forms of altitude training include train-high-live low (THLL), live-high-train-low (LHTL), or an intermittent form of altitude training.

But, how exactly does altitude training aid endurance levels?

Physiological effects of altitude training:

One of the most desirable physiological effects of altitude training is the increased production of the hormone erythropoietin in the body. This is more commonly referred to as EPO. Altitudes of around 2000-3000m stimulates erythropoiesis in the body which increases the erythrocyte (red blood cell) volume (Płoszczyca et al., 2018)

An increased volume of red blood cells means more oxygen can be transported around the body due to an increased oxygen carrying capacity of the body. Research has shown that erythropoiesis can begin to occur within hours of intense altitude training (Eckardt et al., 1989; Knaupp et al., 1992; Rodríguez et al., 2000; Mackenzie et al., 2008  as cited in Płoszczyca et al., 2018). However, it can take up to 4 weeks to completely acclimatise to the change in altitude and reap the most benefits.

Other physiological adaptations to altitude training include increased mass of red blood cells, improvements in the biochemical structure of skeletal muscle, improvements in mitochondrial V02max ,elevated muscle buffering capacity and improved efficiency of muscular contractions (Vargas-Pinilla, 2014)

A more unknown benefit of altitude training is weight loss, which may be beneficial for those sports which have a high focus on weight categories or an optimum weight. Resting metabolic rate (RER) is highly influenced by the environment, with special influence occurring under altitude. Research has shown that a 4 week period of classic altitude training can increase RER by up to 27% (Butterfield et al., 1992 as cited in Woods et al., 2017) in obese patients, a finding which has also been demonstrated in elite endurance athletes (Woods et al., 2017). Although much of the understanding of the mechanism behind this is unknown, it is speculated to be caused by changes in thyroid activity (Hamad & Travis, 2006) and changes in the hunger hormones leptin and ghrelin.

Overall, these benefits can lead to substantial improvements in sport performance, primarily those more endurance based.

Longitudinal studies to test the effectiveness of altitude training has found mixed results, with the classic protocol of live-high-train-high being disregarded as the best strategy. More recent research has demonstrated that the protocol live-high-train-low is the most effective and has the greatest benefit on endurance training and also helps prevent detraining on return to sea level. A study by Levine and Stray-Gundersen (1997) found “Four weeks of living high-training low improves sea-level running performance in trained runners due to altitude acclimatisation (increase in red cell mass volume and VO2max) and maintenance of sea-level training velocities, most likely accounting for the increase in velocity at VO2max”. This finding has been widely supported within altitude training literature and it is now been found to be more advantageous to live-high-train-high (LHTH) as it allows for the acclimatisation and the ability to train at the same intensity and power as would be normal for each individual athlete (Fulco et al., 2000)

But what are the consequences of altitude training?


Pitfalls of altitude training:

Although many advantages of altitude training and hypoxic conditions have been demonstrated, studies have shown the LHTH method can be counterproductive as it reduces athletes ability to train as intensely, meaning when they return to sea level they are often detrained. (See A recent meta-analysis which examined physiological responses of adults training at altitude found an inadequate training volume at altitude, which may be due to differences in climatic conditions which can prevent athletes from being able to train as intensely, is likely to lead to little improvement in athletes haematological variables post altitude training (Płoszczyca et al., 2018). Additionally, it may even be the case that due to genetic variability, some individuals respond more or less to hypoxic stress than others. This individual variability of haematological adaptations can differ around several hundred percent between individuals (Li et al., 2002) and can mean some individuals don’t even respond to altitude training at certain heights. These individuals are known as non-responders and to date there is currently no tool available to determine whether a certain individual is a non-responder. Therefore, although there are clear benefits of training at altitude following the LHTH or LLTH method, evidently this technique would not be beneficial for everyone.

One of the big disadvantages of any of the altitude training methods is the small window of time it provides you with these additional physiological adaptations. Research has shown that these benefits only last up to around 3 weeks after the return to living and training at sea level. Therefore, timing of altitude training is vital to ensure that these adaptations are still present should you be aiming for that big performance PR.

To conclude, recent research has stressed the belief that the LHTL method is now the best form of altitude training, whereby athletes descend from altitude to train then return to altitude to live. This has been shown still provide the physiological adaptations that occur at altitude, but with the reduced consequence of athletes becoming detrained on return to sea level. (See Brocherie et al., 2015; Gore et al., 2001)

Replicating altitude training in everyday life:

It is clear that only some individuals have the opportunity to undergo real life altitude training, but there are some techniques that have become popular that will help to incorporate some of the aspects of altitude training into normal training at sea level. Firstly, breathing exercises have been shown to help improve your lung capacity and hence improve your body ability to intake oxygen into the muscles. These include diaphragmatic breathing and pursed-lips breathing. Secondly, one technique which is much more accessible to the majority of people is conducing some kind of hill training which involves ascending and descending up some altitude.

Although this may not be much altitude (depending on how big the hill you can find is!), these tiny changes on oxygen partial pressure can aid your training and help prepare your body for higher altitudes should you have the opportunity to experience some kind of real altitude training. Finally, more recently, the development of altitude masks have been a huge breakthrough in helping to replicate some of the physiological demands of altitude training without actually ascending up altitudes. Although these masks don’t replicate the actual climatic changes that occur at altitude (e.g. changes in partial pressure of oxygen), they do have some benefits which include inspiratory muscle training, increase in ventilatory threshold and increased respiratory compensation threshold. Essentially these will help you to breath better and intake more oxygen per breath, which helps your muscles perform and recover.

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