With the 2014 World Cup in Rio rapidly approaching, it is of great interest to reflect of the 2010 World Cup winners, Spain, and what may have helped them achieve victory over the Dutch. Throughout the World Cup, many teams reported difficulty with the playing conditions, particularly at altitude. The stadium in Pretoria (South Africa) otherwise known as “Soccer City” and home to the finals matches is at a height considered to be of higher altitude (1753 metres, or 5752 feet). Spain, the world cup winners had prepared for this type of environment at their world cup campaign training at their facility located in Sierra Nevada, at a height of 2320m, or 7611 feet (Millet 2010). Over the past four years, altitude training has received greater support in other codes of sport including rugby and Australian football (AF). This article with examine the scientific basis for utilising altitude and the hypoxic environment as a strategy for improved physiological functioning.
Hypoxia in Sierra Nevada (or equivalent), at 2300 metres, stimulates an immediate increase in respiratory ventilation. This hyperventilation causes a decrease in the arterial pressure of carbon dioxide, which induces a disturbance in the acid-base balance within the lungs (Gillam 2013). This may be the basis of some possible nausea, irritability and insomnia when first arriving at a higher altitude.
Altitude challenges the body to respond to reduced oxygen partial pressure which requires increased pulmonary, cardiovascular and metabolic function. At increased levels of altitude it is known that haemoglobin saturation decreases, with saturation at 1750m reaching 95% (as per http://www.altitude.org/oxygen_levels.php). Athletes at 4300m experience 80% saturation compared with 96% at sea level (Wilber, Stray-Gundersen et al. 2007). Further, there is a reduction to 75% in the diffusion from the blood to the muscle tissues. Total blood plasma volume is reduced by 25% and there is a subsequent increase in the concentration of the red blood cells with more oxygen delivered to the muscles per cardiac output. The sympathetic nervous system responds to the increase in altitude by releasing norepinephrine and epinephrine, two cardiac altering hormones. In response, the cardiac output is increased, particularly at rest and during sub-maximal exercise (Wilber, Stray-Gundersen et al. 2007). Decreased mitochondrial function and glycolytic enzyme activities cause the cross-sectional area and total muscle area to decrease, whilst the capillary density within the muscles increases. This allows for more oxygenated blood to be muscle fibres and can be a danger if appropriate nutritional strategies are not implemented (Wilber, Stray-Gundersen et al. 2007).
Acclimatisation or adaptive response to altitude:
Generally, it can take between seven and ten days to acclimatise to altitude. Research shows that during this time athletes should focus on increasing volume rather than intensity of training. Continued exposure, greater than fourteen days, stimulates the production of erythropoietin (EPO) from the kidneys (Wehrlin, Zuest et al. 2006). EPO acts by increasing the total number of red blood cells with evidence that athletes living at 2500m and training at 1800m for 24 days, increased their haemoglobin mass and red blood cell volume by approximately 5% (Wehrlin, Zuest et al. 2006). Although this study, reported a 5% increase overall, a recent review highlights that the variability within individuals, in terms of their responses to hypoxia and erythropoietin (Gillam 2013).
Prior conditioning is vital when attempting to acclimatise and train athletes at altitude. Improving maximal oxygen consumption through training at sea-level prior to altitude has been reported to increase performance and adaptation of athletes at altitude (Lundby, Millet et al. 2012). This sea-level training can be of a higher intensity than altitude and, hence lead to improved performance when at higher altitudes. It is recommended that athletes commence altitude training at 60 to 70% of sea-level intensity to account for their reduced working capacity. As maximal exercise capacity is reduced under hypoxic conditions, training at altitude at the same absolute intensity as at sea level represents a larger stimulus that could eventually lead to training maladaption and an increased likelihood of adverse signs and symptoms, such as altitude sickness (Bonetti and Hopkins 2009). The concept of ‘live-high, train low’ has received substantial support given the advantages of maintaining intensity when training at sea level, whilst obtaining the haematologic adaptations (increased erythrocyte volume) by sleeping at altitude (Wehrlin, Zuest et al. 2006, Lundby, Millet et al. 2012). The added advantage is the affordability of setting up simulated environments such as hypoxic tents or building hypoxic rooms where oxygen extraction or nitrogen enrichment allows athletes to gain adaptations without needing to organise expensive training camps overseas, a concept which appears to be supported in some sports (Gillam 2013).Studies investigating ‘live high-train low’ generally concede this method as helping some, but not all, athletes in improving their performance. It is agreed that natural altitude appears to be more efficient than artificial hypoxia and the observed improvements are roughly around 1 to 2% (Bonetti and Hopkins 2009).
Elite teams sport athletes such as soccer, rugby or Australian Football (AF) players, often need high aerobic and anaerobic capacities, as well as high proficiency in technical and tactical skills, to be successful in their sport. These athletes usually possess a total haemoglobin mass of 11g.kg-1 within or slightly above the normal range (10 to 11 g.kg-1) (Bonetti and Hopkins 2009). Thus, it is reasonable to expect that a ‘live high-train low’ method may substantially increase their red blood cell synthesis thus increasing the athlete’s haemoglobin mass, therefore reinforcing their aerobic capacity (Bonetti and Hopkins 2009).
Although the 2014 World Cup is not being held at the same height of altitude as the 2010 World Cup in South Africa, altitude training may be one environmental conditioning strategy used to improve aerobic function in elite football players. This article has providing some scientific basis as to how and why such training methods can be beneficial. Training in the heat is also now being used by elite sporting teams as an environment to improve physiological functioning in preparation for the 2014 World Championships in Qatar, and this will be explored in a subsequent article.