In the third of our four-part series on acclimatisation, Jamie Macdonald (high altitude physiologist at Bangor University) and Calum Muskett (professional climber and mountaineering instructor), delve into the complex and controversial world of rapid acclimatisation to see whether 'quick fixes' can replace or assist the classical slow ascent acclimatisation profiles.

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The Siachen glacier, on the border of Pakistan- and India-controlled Kashmir, has been described as the world's highest battleground. Conflict began in 1984 with the Indian army's Operation Meghdoot, in which they gained control of the entire Siachen glacier. The glacier itself is the longest in the Karakoram at 76km, and ranges in altitude from 5,753m to 3,620m where it borders China. In the 19 years following Operation Meghdoot, intermittent combat operations at extreme altitudes by both militaries would define this conflict, before the cease-fire of 2003. Even in the years following the cease-fire, the high mountain environment has claimed the lives of over 300 military personnel and overall; estimates put between 70% and 97% of casualties of this conflict down to avalanches, weather and altitude.

The extreme physical challenges of this conflict are well understood by high-altitude physiologists and mountaineers. In most circumstances, individuals must ascend to such high altitudes under their own steam, that is to say, on foot from where the roads, cable cars and mountain funiculars terminate. In Siachen, the rapid deployment of troops has precipitated the need for the highest helicopter pad in the world, in which troops are shuttled to and from this troubled region. Unconfirmed sources have estimated that for every one troop rapidly deployed, another is almost immediately evacuated due to altitude related sickness.

The Siachen conflict is not the only instance of recent high-altitude warfare. The mountainous region of eastern Afghanistan has also seen a number of high-profile cases of mountain warfare, especially following 9/11. These operations, led by coalition forces, served to highlight the importance of acclimatisation as troops, dressed for desert warfare, were dropped in the snow at altitude and suffered, in some instances, from debilitating altitude sickness. With the assets that the US and UK militaries have to offer, it comes as no surprise that in the years following these conflicts, millions of pounds have been poured into acclimatisation science, concentrating on the Holy Grail of acclimatisation research: how to safely achieve rapid deployment to high altitude.

In this age of soundbites, Instagram and instant news we are often in a rush to achieve our objectives in the shortest time-frame possible. Social media is full of videos on how to learn to wheelie in one hour, idiots' guides to programming, and how to train for your first 8a sport route. Unfortunately, as many of us have discovered, the bold claims made by these catchy titles often seem impossible to achieve. As described in our previous article, successful acclimatisation takes time to achieve, but for many of us, summiting a high mountain remains a race against time. Limited holiday, lack of money and goal-induced blindness put pressure on us to find shortcuts and we are easily led to believe bold claims. So which (if any?) of the different drugs and the increasingly widespread availability of hypoxic and hypobaric chambers should we consider?

Hypoxic chambers

In 2016, the American couple Adrian Ballinger and Emily Harrington climbed Cho Oyu (8,201m), just nine days after leaving their home in California. This lightning-fast ascent, which may be the shortest acclimatisation to an 8,000m peak, was attributed to training and sleeping at home in hypoxia (reduced inspired oxygen content) using hypoxic chambers to fast-track their acclimatisation process. Ballinger and Harrington trained carefully, monitoring statistics such as heart rate and blood oxygen saturation to moderate the balance between training, pre-acclimatising and recovering. Whilst it should be noted that Ballinger and Harrington are both professional athletes with previous high-altitude experience, and had the aid of Sherpas, lightweight equipment, a good weather window and supplementary oxygen, the use of pre-acclimatisation using hypoxic chambers may have contributed to their successful ascent.

Ballinger and Harrington's ascent of Cho Oyu demonstrate what can be achieved when high levels of fitness and planning are combined with a scientific approach and commitment to a rigorous training regimen, but can this be applied to the everyday trekker and alpinist? To buy personal hypoxic generating equipment and the like are not cheap, with starting prices in the region of £3,000 for a tent and generator. If you're lucky, you may have a hypobaric chamber at your local university you can use. But you can now get access to hypoxic chambers on an hourly basis through commercial offerings available in many major cities and it is even possible to rent hypoxic generators and altitude tents to use at home. So what length of time do we need to spend inside them and do they really help?

Evidence suggests that pre-acclimatisation using altitude chambers can help. However, the amount of exposure (height and time) needed to have a benefit is substantial and may be unrealistic for many. Even when studies have investigated more than 8 hours of simulated altitude exposure per day for a week or more, benefits have been slight, and there are clearly problems following such a programme when we need to work and complete daily activities. The issue is that it is difficult to provide a sufficiently high dose of altitude using home-based systems: simulated altitudes within an altitude tent are often less than 3000m and although higher heights can be obtained using a mask, these are uncomfortable to use for periods of longer than an hour. Meanwhile, in-centre-based systems do not practically allow sufficient exposure time. Even sleeping in chambers has not realised the expected effect, and the disadvantages (disrupted sleep due to the noise and heat generated in the altitude tent) may outweigh the small advantages. Jamie's wife became acutely aware of this latter problem when made to sleep in a tent before travelling with Jamie to La Paz, Bolivia…

One way commercial companies have tried to circumnavigate this issue is to offer exercise sessions (particularly short duration high intensity, or HIIT) in their commercial chambers. The benefits of this approach remain unknown. On the one hand, the theory goes that an increased training stimulus may be possible if you exercise as normal but breath hypoxic air at the same time. On the other hand, the absolute amount of training you can do will be lower (i.e. when breathing hypoxic air, you turn down the intensity on your exercise machine).

For now, evidence to back up the use of hypoxic chambers exists, but only if you can invest a significant amount of time and money to get a sufficiently high dose…

Performance enhancing drugs

The world of outdoor climbing and mountaineering is nuanced and not subject to the same regulations and anti-doping rules as competitive sports. There is also significantly less financial incentive to "cheat" in climbing, a regular driver for those famous cases involving some of the top controversies in world sport. With that said, climbers and mountaineers have realised they may benefit from some of the most widely used performance enhancing drugs (PEDs) in competitive sport, e.g. to increase oxygen delivery to the muscles (blood-doping) and/or to enhance muscle strength (steroids). In fact, in the competitive sports of sky running, ski mountaineering and bouldering, athletes have already been caught using PEDs.

Whilst we might not expect or imagine recreational alpinists will be going to such extreme measures as blood doping to increase their chances of summiting, in a study carried out from the Goûter and Cosmiques refuges on the "Voie Normales" of Mont Blanc, 430 pee samples were analysed anonymously from the urinals to discover that 36% of alpinists were using at least one drug. Two of the most commonly detected drugs were acetazolamide (Diamox) and the sleeping medication zolpidem.

Different drugs can be used as treatment or prophylaxis, and may help in different ways, potentially decreasing symptoms or aiding acclimatisation. However, all drugs come with a large cautionary note including side-effects, masking of symptoms of altitude illness, and possible decreases in performance. Further information on this fascinating but controversial topic is available here.

"Beeting" altitude sickness: dietary advice

Whilst drugs and hypobaric chambers may seem like a rather extreme approach to boosting altitude performance, there are other, more modest methods that have grown popular in recent years. Amongst the most popular have been changes in diet to incorporate a larger consumption of nitrate rich foods. Some of these, such as beetroot, garlic, leafy green vegetables and dark chocolate, are nitrate rich and the body can convert these nitrates into nitric oxide - a molecule we learnt about previously in article two, which is present in higher concentrations in Tibetans and allows normal blood vessel function to enhance oxygen delivery. At altitude, the body struggles to produce nitric oxide and therefore boosted levels of nitrate consumed in food can positively combat this decline in nitric oxide production.

With the caveat that a balanced diet is likely to include more than sufficient levels of nitrate rich foods, some scientific studies have found that the consumption of nitrate rich beetroot juice may restore reduced blood vessel function in healthy adults at altitude. Some findings have even shown reduced acute mountain sickness (AMS) and enhanced performance in participants consuming beetroot juice compared to the control groups. Unfortunately, field studies are difficult to run, and despite the scientists' best efforts, these studies were not vigorously conducted and their benefits should be interpreted with caution. Those who are already fit or have a healthy diet are less likely to get a beneficial response, and some studies even suggest using beetroot juice may increase risk of altitude illness. So, despite being a cheap and seemingly safe method to enhance performance, dietary manipulation of nitrate intake cannot be recommended at present.

No discussion on diet would be complete without mention of macronutrients (carbs, proteins and fats). Special diets are becoming more popular. Scientific evidence remains sparse, but these diets have advocates, such as Dave MacLeod using "Ketogenic" diets which are typically high fat, medium protein and low carbs. However, without input of a sports nutritionist, it is very easy to get these diets wrong and hamper performance. Alpinism is an endurance game requiring a constant but often slow release of energy. The simplest advice to give is that a balanced diet with enough calories consumed and at the right times will keep our body functioning as well as it can under the physiological strain of arduous mountaineering activity at altitude. Crucially in alpinism, the altitude and cold conditions are likely to make eating and drinking problematic and unappetising, despite your metabolic rate increasing with altitude. It's of the utmost importance to watch your fluid and food consumption to keep on top of this on the mountain.

Whilst a deeper understanding of complex nutritional strategies may prove valuable for the marginal performance gains, starting with a balanced healthy diet, and gaining a simple understanding through personal practice (trial and error) of what works for you, ensuring you consume food pre, during and immediately post mountaineering activities, will have a far greater impact upon your performance. If you really want to enhance endurance performance through diet manipulation, carbohydrate supplementation (drinks, bars, gels, and unprocessed foods such as wholewheat pasta, bread, rice) remains the most evidenced and easily applied intervention.

A final dietary supplement that warrants a mention is caffeine. The evidence for caffeine having a positive effect on physical and cognitive performance is very strong. Almost all studies unequivocally suggest it decreases sense of effort and increases endurance exercise capacity. Admittedly it can act as a mild diuretic, increasing urine production, but studies suggest that at normal doses (as consumed in coffee and tea) this effect is normally outweighed by the increase in fluid intake from the water used to make the tea or coffee. Caffeine is also available in gels and energy drinks. We often use it towards the end of a long mountaineering day when fatigue is setting in and you just need to watch your step to catch the last gondola.

In the final article in the series we will investigate how to physically prepare yourself for high-altitude mountaineering to make the most of your time spent in the mountains.