How attitudes to altitude training are changing

Thirty-three days. That was all the time Tadej Pogačar had this year between sealing his Giro d’Italia victory and the start of the Tour de France. In that time he spent three weeks at Isola 2000 in the French Alps.

As has become commonplace, Pogačar sought out high altitude in the hunt for a competitive edge, but the thinking and strategies behind altitude training are evolving all the time. It’s no longer enough to simply spend a lot of time at the top of a mountain…

Benefits to the blood

Iñigo Mujika is one of the world’s leading applied physiologists, with a PhD in the biology of muscular exercise and another in sports science. Away from academia, he was head of training at the Euskaltel-Euskadi pro team (version one) and is now an advisor to the Japan High Performance Sports Centre. He specialises in tapering and altitude training.

‘When cyclists head to altitude, which is around 1,500m to 2,500m, they’re looking for haematological benefits, the most important of which is an increase in haemoglobin mass,’ says Mujika. Haemoglobin is a protein in red blood cells that binds to oxygen. At altitude, the body’s strain for oxygen sees it crank up levels of the hormone EPO (erythropoietin) to produce more red blood cells to cling onto oxygen.

‘This increases your VO2 max,’ says Mujika, ‘but it doesn’t always work for everyone. Some riders might go to altitude for up to four weeks and see no change in haemoglobin mass. But that doesn’t mean the camp wasn’t useful because there are many other adaptations that boost performance. These include a greater capacity to transport and utilise glycogen, plus a greater buffering of lactate, so you can theoretically pedal harder for longer.’

Teams track these adaptations via a range of implements. ‘Every day we use a pulse oximeter to measure the saturation of oxygen in the blood,’ says Ineos Grenadiers coach Adrian Lopez. ‘If you’re 98% at sea level, that might drop to 92% early in an altitude camp. How a rider feels with that drop is an individual thing – they might feel fine, they might feel terrible – but as time at altitude progresses, that figure should rise as they adapt. The riders also have blood tests at the start and end of a camp, with most adaptations happening in the first 20 days.’

This has been the basic template for altitude training for a number of years, however it is only relatively recently that greater emphasis has been placed of the frequency of altitude camps.

Periodisation of altitude training

Back in 2019 Mujika co-wrote a groundbreaking paper entitled Contemporary periodisation of altitude training for elite endurance athletes: a narrative review.

‘In it we argue that there should be a long-term approach to altitude training – an athlete should go to altitude multiple times over the course of a season to maximise the gains,’ Mujika says.

Since that paper an increasing number of teams and riders are exposing themselves to significant bouts of altitude, from both living high and repeated altitude camps. Before the 2021 Tour de France, Mathieu Heijboer, Jumbo-Visma’s performance director and then coach of Primož Roglič, told Cyclist how that season the Slovenian had endured breathless camps in both Tenerife and Sierra Nevada followed by seven weeks at altitude in Tignes, France.

‘There’s evidence that repeated altitude camps, during a single season or across multiple seasons, means that the body is exposed to hypoxia more often, which is more beneficial in terms of increasing red blood cell count than one or two camps,’ Heijboer told us. It’s called ‘hypoxic memory’ and should enable riders to acclimatise faster to subsequent camps, resulting in a greater workload and stronger outcome.

That’s the theory, although it is challenged by the notion of responders and non-responders – that some riders enjoy the physiological and performance benefits of altitude and others don’t. This fact is reflected by a 2020 paper in the Scandinavian Journal of Medicine and Science in Sports where a Finnish team showed that of 15 athletes who’d undertaken altitude camps at least twice, 27% always enjoyed positive haemoglobin responses, 13% negative and 60% a mix of both.

‘This variability warrants efforts to control numerous factors affecting an athlete’s response to each altitude training camp,’ the paper concluded, something that Mujika wholeheartedly agrees with.

‘To avoid mistakes that hinder adaptations we use the five “I”s,’ he explains. ‘The first “I” stands for iron. You need sufficient iron stores in your body to support the enhanced erythropoiesis production of red blood cells. That generally means an iron supplement at altitude. The second “I” is for intake. That means sufficient carbohydrate to cope with the training and sufficient protein to facilitate adaptation.

‘The third “I” is illness,’ Mujika continues. ‘Take all possible measures to avoid sickness. That means factors such as good recovery, good nutrition and good hygiene. It’s easy to fall ill with the extra strain of altitude. Four is injury. If you head into a camp with a niggle, causing inflammation, that hinders the adaptation process.

‘The final “I” stands for intensity. When you arrive at altitude, training shouldn’t be too intense, especially if you’re inexperienced up high. There should be a monitored increase in workload as the camp progresses.’

The altitude sweetspot

We can add an ‘E’ to that: experience. Earlier in the year Cyclist spoke to Simon Yates, who told us he’d adapted his altitude strategy: ‘When I first lived in Andorra I moved straight up to altitude, so I was training high for most of the year. That paid off to a degree, but it also meant I’d return from a race and not enjoy sufficient recovery. Now I’m spending more time training at sea level to feel fresher as well as undertake really high-quality sessions, day in, day out. I’ll then head higher for key parts of the season.’

Yates’s final Tour de France position this year of 12th, eight places down on his 2023 showing, might suggest the change hasn’t paid off. Then again, his build-up was beset by illness. Still, says Lopez at Ineos Grenadiers, Yates is spot on in noting there’s a balance to be had.

‘When in Andorra, we’ll often drive or ride to the Spanish side for low-altitude work. From a muscular point of view, you can work harder.’

And that’s important, because overdosing on living and riding high can weaken the muscles. This is down to an increase in stress, resulting in cortisol coursing through the rider’s veins. Coritsol is a catabolic hormone, meaning it will start to break down the rider’s muscle, which is not ideal when seeking peak performance.

Mujika suggests this can be offset with hard sessions because they don’t rely on oxygen availability, ‘so you can generate high power outputs even in hypoxic conditions’.

Another option might be to head to somewhere hot. Jayco-AlUla’s Luke Durbridge tells us, ‘I prefer to train at home in Perth [Australia] ahead of the spring Classics rather than head to altitude. I don’t really touch proper altitude until Amstel Gold has passed. In Perth it can hit 40°C. That’s a real heat stress and I know there’s a lot of good stuff coming out about heat’s benefits being comparable to altitude.’

Some like it hot

He’s right. A study out of Coventry University showed that while cyclists training at altitude improved their 16km time-trial time significantly compared to a control group, they only just edged out a group that trained in heat. This, the authors suggested, was down to an increase in ‘heat shock proteins’ that better prepared the riders for the extreme stress of altitude than the comfortable sea-level group.

Another paper in 2022, High or hot – perspectives on altitude camps and heat acclimation training as preparation for prolonged stage races, also highlighted the benefits of heat training, including increasing plasma volume, the liquid component of blood that, among myriad functions, helps the body remove waste and distribute nutrients. Altitude reduces plasma volume via increased EPO production, so the researchers questioned the combining of both as they’re fighting each other.

Instead they suggested, ‘The choice between heat or altitude acclimation may eventually depend on the specific exposure scenario for the given stage race. For example, if several stages with mountain finishes are located in the first part of the race and the risk of profound heat is low, an altitude camp in the lead-in phase may be prioritised. The reverse is true if high heat stress is expected and flatter stages are scheduled in week one.’

Another feather in the heat cap is not only by how much heat training stimulates performance but how long and easily those gains are maintained compared to altitude training, where haemoglobin mass gains are halved within seven days on return to sea level and return to baseline within 14 days.

‘Thus, it’s very important to stress that an altitude training camp should be completed in close proximity to the competitive period,’ the researchers concluded.

However, further research from Daniele Cardinale, head of sport physiology and performance laboratory at the Swedish Sport Confederation, suggests that the benefits of altitude training can be maintained for longer when followed by a good period of heat training.

‘The haemoglobin mass levels of athletes who went to altitude and then did three and a half weeks of heat training were almost the same,’ he says.

Heat training could be used after altitude camps in the build-up to the Tour to maintain the gains. ‘It’s a new tool in the toolbox,’ Cardinale says.

Not always poisonous

When Cardinale presented his findings at the Science & Cycling Conference in Florence this year, he revealed an even more thought-provoking discovery.

‘Going to altitude isn’t always practical, so is there another way?’ he said. ‘That’s when I came across carbon monoxide. It originally scared me because you associate it with danger, with poisoning.’

Cardinale proceeded to explain how carbon monoxide is ‘very clever’ as it binds to haemoglobin with 240 times the affinity of oxygen to form carboxyhaemoglobin. Once bound, carbon monoxide takes several hours to disassociate from haemoglobin, during which time the oxygen-carrying capacity of blood is reduced. This, said Cardinale, resulted in the same surge of EPO as at altitude in the body’s stressful search for more oxygen. In short, carbon monoxide can increase haemoglobin mass and boost performance.

Professor Walter Schmidt of the University of Bayreuth saw similar results a few years earlier. Eleven subjects inhaled a small amount of carbon monoxide five times a day for three weeks and their haemoglobin mass increased by 5%.

As in Cardinale’s study, this increase was accompanied by a measurable increase in endurance performance and corresponded to the effects of altitude training over the same length of time. Several WorldTour teams already have carbon monoxide rebreathing tools, but claim this is to track blood parameters rather than boost them.

Sound dangerous? Carbon monoxide is produced by the body itself and, says Schmidt, in small doses ‘could be a real alternative to altitude training… However, before the method can be adopted in practice, there are ethical questions that need to be resolved and some medical aspects to be researched in more detail’, especially as Schmidt suggests it could have a stronger performance-enhancing effect than EPO doping. It’s also linked to mitochondrial biogenesis and capillary growth, both favourable adaptations for performance.

What does WADA (World Anti-Doping Agency) think about this, seeing as carbon monoxide is not on the prohibited list?

 ‘Exposure to carbon monoxide has been discussed by WADA’s Prohibited List Expert Advisory Group, but there is no consensus on whether it can have a performance-enhancing effect and no sufficiently robust data currently supports that,’ a spokesman told us. ‘It is, however, generally acknowledged that it can be dangerous to use so it would not be recommended.’

This would sit under the umbrella of extreme altitude interventions, and even more extreme than sleeping in an altitude tent tuned to 3,000m on an altitude camp, as suggested by Mujika.

Altitude training is evolving, driven by ever-smarter management of altitude blocks, management of training workload, inclusion of heat training and the potential use of carbon monoxide for performance purposes (though we suggest this last one may be batted away forever more by teams who realise it’s not a great look, even if it is currently not prohibited). The altitude camp is set to become an ever more important tool in the pro team’s armoury, and its benefits extend beyond the purely physiological.

As Durbridge says, ‘Despite all that’s said about the benefits of altitude camps, I feel the “camp effect” is arguably greater. You’re cooked for, there’s a great focus on sleep, there are no distractions, and there’s massage on top. For me, that’s the big win.’

• This article originally appeared in issue 157 of Cyclist magazine. Click here to subscribe