Laura Lewis has a degree in Sports Science and a PhD in Exercise Physiology and researches altitude training and the haematological adaptations to training and stress. Also a highly accomplished runner, Laura has a marathon PB of 2:56:53 and a 10,000m PB of 37:27. She is the sister of Buccaneer crew member Elaine.
Altitude training used to be a pilgrimage for the truly elite but in todays’ world it is becoming much more mainstream and accessible for all athletes to incorporate altitude into their training plan, be it weekend warrior or aspiring Olympian. Although the blanket term altitude training is often used, it is worth noting that there are a number of different types of altitude training with the adaptations and accompanying benefits (or not!) varying quite a bit between the modalities.
First it’s important to differentiate between natural, or “real” altitude, and simulated or artificial altitude. At natural altitude, the decreased barometric pressure decreases the partial pressure of oxygen in the air and thus the amount entering the lungs. In a simulated environment, the amount of oxygen in the air is lowered, often by adding extra nitrogen, but the air pressure remains normal. The other key difference is whether you are training or resting in the altitude environment. Some modalities combine both. The key point here is that the adaptations associated with either training or resting at altitude differ greatly.
Effects of altitude
When exposed to an altitude environment, the low partial pressure of inspired oxygen initiates a number of signalling cascades throughout the body. The most famous of these pathways involves the two key signalling proteins of HIF1 alpha and erythropoietin (EPO). If the signal is strong enough and persists for long enough, EPO stimulates the production of extra red blood cells (RBCs) in order to increase the amount of oxygen which can be transported around the body, thus compensating for the reduced amount of oxygen available. When we return to sea level these extra RBCs serve to increase our maximal oxygen transport capacity allowing us to do more and potentially improve our performance. The key aspect of this haematological adaptation to altitude exposure is that it requires a minimum dose of exposure to initiate and takes at least 10 days before meaningful changes in RBCs can be detected. This has implications for the optimal duration for altitude training camps. Altitude training can also result in a number of non-haematological adaptations which can contribute to enhanced performance at sea level. These are often harder to measure than an increase in RBCs but may be equally, if not more, important. These adaptations include improved muscular efficiency during submaximal exercise and an increased muscle buffer capacity meaning changes to muscle and blood pH can be better tolerated.
Types of altitude training
The four main types of altitude training are as follows:
Classic altitude training, also known as Live High, Train High (LHTH)
Athletes have been living and training “up a mountain” for numerous years. Athletes spend 24/7 in the altitude environment, with all training conducted at the altitude venue as well as day to day living. Natural altitude has recently been classified as follows: < 500m near sea level, 500-2000m low altitude, 2000-3000m moderate altitude, 3000-5500m high altitude, >5500m extreme. Most athletes will conduct natural altitude camps at low to moderate altitude with the optimal height for living and training considered to be 1800-2500m (e.g. Flagstaff USA; St Moritz, Switzerland; Iten, Kenya) for 2-4 weeks. This altitude is considered high enough to stimulate RBC production but not so high that training quality and intensity is excessively compromised.
Live high, Train Low (LHTL)
This approach became popular following a study by US researchers who found that athletes who performed their training at a lower altitude to that which they slept at, performed better at sea level than those who lived and trained high all the time. By descending close to sea level for high quality sessions, it was believed these athletes were able to get a better training effect whilst still reaping the benefits of sleeping at altitude. LHTL altitude training can be performed using natural or simulated altitude. At natural altitudes, travel logistics might make descending for training difficult. Therefore, some sporting institutes have created Altitude houses or hotel rooms for athletes to live and sleep in so that all of their training can be conducted at sea level in their normal environment. The same principle applies to altitude tents, which are now readily available (for a price!) The key to a successful LHTL model is the total hypoxic dose you are exposed to when “living high.” Here, both the severity of altitude and the amount of exposure each day are important.
Current research recommends 14h /day at 3000m for 3 weeks which can be somewhat of a challenge to achieve using small tents. However, shorter exposures are unlikely to stimulate RBC production and will just end up burning an unnecessary hole in your pocket!
Intermittent Hypoxic Training (IHT)
In an attempt to make altitude training more accessible, many facilities have opened up offering athletes the chance to train at altitude. These altitude training rooms create a simulated altitude environment much like that in which you would sleep, but the idea being that only individual training sessions are performed, and thus being far more time efficient. Many companies will market these rooms as a way to increase RBC production. It’s important to understand that the mechanisms underlying IHT are different from LHTL or LHTH. The exposure time is too short to initiate erythropoiesis so this approach should not be considered an alternative to sleeping at altitude.
Of course, training in hypoxia is challenging and can be used an extra training stimulus. Some research has found evidence of changes at a metabolic level but has struggled to link these to improved performance, particularly in elite athletes. Perhaps the best way to incorporate IHT, is to combine with LHTL, so that some sessions are performed “high” similar to a conventional altitude camp. Another potential use is when returning from injury, since a high metabolic load can be achieved without a high mechanical load due to the extra energy cost associated with any given workload.
Intermittent Hypoxic Exposure (IHE)
Intermittent hypoxic exposure refers to breathing a hypoxic gas through a special device for a short period of time (1-2 hours) at rest. The gas mixtures used usually simulate high to extreme altitudes with the idea being to create a hypoxic dose high enough to stimulate RBC production in a short period of time. Unfortunately, this method is not backed up by science, with the exposure simply being too short. Those 1-2 hours would be much better spent sleeping, in my opinion.
Why do various sports use it?
Altitude training used to be a training tool only for endurance athletes, but is now becoming popular with many disciplines including team sports and more anaerobic sports such as sprinting. There are several reasons for using altitude and the timing of the altitude stint relies on the main goal of the camp. Pre- or early season is a very popular time, with altitude used to accelerate base phase adaptations and essentially get an athlete fitter, quicker. The same could also be said in the middle of the season after a short break and is an approach often used by professional cyclists around June / July. Others use altitude training specifically before a competition in an attempt to enhance their performance at sea level. This is a “high-risk” strategy as the optimal time for peak performance post altitude is highly individual and may take many attempts to work out. Some athletes compete best immediately after exposure whereas others find the magic window somewhere between 2-3 weeks. If this is an approach you are considering, then some careful trial and error is advised before the big competition.
My favourite way to use altitude is to use it as a training platform to allow you to train at a higher level once back at sea-level. In this way, best performances might be seen as long as 6-8 weeks after the altitude stint, thanks to the superior training that was performed with the assistance of those new-found adaptations.
How can age group athletes incorporate altitude training into their training?
For me, there is nothing better than a trip away for a training camp in the mountains. Whether it’s the altitude that has an effect on your performance or merely a “training camp” effect from spending 2-3 weeks solely focussed on your training in a new and uplifting environment is debatable, but does it really matter? If you have the time and can afford it, this is how I would use it. Altitude tents are the next best option, but make sure you (and your partner!) are willing to invest the time needed to build up the optimal exposure hours. Whichever modality you use, make sure your first exposure is well away from competition. Take it easy in the first week of exposure to allow your body to adapt and make sure your iron intake and nutrition are up to scratch.
Racing at altitude
Racing at altitude can be another kettle of fish entirely. The Mexico City 1968 Olympics were a perfect case in point of how different events are affected by altitude. World records were broken in jumps, throws and running events of up to 400m where the decreased air resistance associated with the altitude were actually an advantage. For the middle and long distance events it was a different story and even the altitude natives struggled. It’s pretty safe to say that reduced oxygen availability is not conducive with setting fast times or recording PBs in aerobic events. Whilst the IOC has agreed never to hold a summer Olympics at altitude again, many sporting events are held at low to moderate altitude and the Ironman calendar includes races at Lake Tahoe and Boulder, Colorado, where altitude will be a significant consideration. If you plan to compete at altitude and have particular goals in mind, it’s worth taking note of a few key points.
Respect the altitude – you can’t just ignore it.
It’s amazing how many athletes, professional or amateur, believe that the “fly in-fly out” approach will actually work. Popular with football teams, this approach essentially involves spending as little time at altitude as possible, flying in literally hours before the competition in an attempt to sneak under the radar in the hope the altitude won’t know you’re there. Apart from being logistically near impossible for a triathlon event, the science shows that this approach is flawed. The lower partial pressure of oxygen in the air is detected immediately upon arrival at altitude and as a result the amount of oxygen transported in arterial blood is also decreased. The end result – a decreased aerobic capacity and increased oxygen cost at all workloads. The good news is that if you accept that altitude will affect you, it’s possible to do something about it.
Try to maximise adaptation
If you can, aim to live and train at or as close to the altitude you will be competing at for at least 2 weeks. This can be expensive, but so too I imagine is the plane ticket and entry to the event. Full acclimatization to altitude takes months to years but fortunately, recent research shows that worthwhile adaptions are present even just 2 weeks of exposure to the altitude environment which contribute to better performances.
Adjust Pace during or lengthen recovery between efforts
If you hadn’t noticed it at rest, then the lack of oxygen at altitude certainly catches up with you when you start to exercise. Your heart rate and perceived exertion will almost certainly increase for any given workload and lactate will start to accumulate much earlier. It’s important to recognise this so you can adjust your pacing accordingly. Depending on the altitude, your speed on the bike might still be quite high due to decreased air resistance, but the power you can sustain for long periods will be lower. Short duration efforts can usually still be performed at a high quality but unless you lengthen the recovery between efforts you will pay quickly for this. Altitude is definitely a place to save those matches for later in a race…
Focus on hydration and nutrition during as well as after exercise
You will find you can become dehydrated much more easily at altitude. An increased breathing rate even at rest results in more water lost through breath. It is therefore important to make sure you stay hydrated during and after exercise. Try to keep on top of your fluid intake throughout the day, but back off after dinner otherwise you will find yourself getting up many times during the night. Beware of the dreaded hunger flat at altitude too; altitude changes the way we metabolise fuel, particularly at lower intensities, so you may find you need to eat more during a session. Don’t try to actively lose body mass at altitude as this will dampen your ability to adapt to the environment.
To finish, here are what I consider to be the keys to a successful altitude camp – the athlete must be:
Healthy, happy, injury free, iron-sufficient, energy balanced, fatigue-free and ready to train.