Altitude training has long been a fixture for endurance athletes. It has been common for riders to head for the mountains for some time. As well as familiarising themselves with the local passes and working on the pedal stroke riders are also subject to hypoxia or oxygen deprivation, triggering a set of responses in the body.
But riders need not go to the high mountains for this. It is possible to sit at home yet experience the conditions of altitude thanks to what is commonly known as an altitude tent.
They say there is less oxygen at altitude but this is false, the mix of gases in the air is the same. Instead the higher up a you go the air pressure gets lower. Consequently the partial pressure of oxygen is reduced. An altitude tent does not copy this change in pressure. Instead it pumps refined air with a reduced oxygen content into a confined space.
Go to the mountains and the effects become measurable above 1,500m and noticeable above 2,000m. Even if you are seated and idle the breathing quickens and the heart rate increases, outward signs of hypoxia. If you spend time at altitude there are longer term responses. The blood chemistry changes and in time the idea is that the body responds to the hypoxia by producing more red blood cells which help carry oxygen. Typically at least two weeks is needed, if not three weeks before this happens to a significant degree. When the athlete returns to sea level the increased concentration of red blood cells will decline, but over weeks giving them a greater ability to transport oxygen than before.
That’s the basic theory but the science appears a lot more nuanced. First some respond better than others. Next the haematocrit, the concentration of red blood cells, can fall at first before rising. Some claim the thicker blood is harder to pump around the body but these studies probably have not seen pro cycling in the 1990s. It is also said the acidity of the blood changes for the worse for athletes and that muscle tissue can wither.
In summary there can be gains for some but if these are significant, they are not quite transformational. The achievable increase in red blood cells is substantially lower than illegal means like EPO use or blood doping.
An altitude tent uses a home oxygen concentrator. These machines were developed for the sick needing extra oxygen at home. The concentrator sucks air in via an intake and then uses chemistry to remove nitrogen from the air, with two exhausts, one with the concentrated stream of oxygen for the patient and the other with the unwanted nitrogen.
The athlete uses a modified version. Whilst the sick patient gets concentrated oxygen via a pipe from the unit, the athlete reverses this and connects a pipe to the exhaust where the nitrogen is piped into a sealed space. Often a type of tent is used so that the oxygen reduced air can be pumped in. Sometimes the athlete will convert a room at home to make it almost airtight. This can be DIY-style with tape around the windows and doors but in some cases athletes have had built specially-designed rooms with specially sealed doors.
The air inside the tent or room is monitored to ensure the oxygen level is correct with a simple device used by scuba divers to check their air tanks. For example to simulate 3,000m above sea level the oxygen concentration is reduced from the normal 20.9% you get at sea level to around 15%.
How Is It Used?
This varies. Some will train outdoors and then return to rest and sleep in the hypoxic conditions. Others might exercise inside a chamber or use a mask to supply rarefied oxygen/nitrogen mix whilst they ride indoors. But it seems the tent is the most common use with it being placed around the mattress. The athlete climbs in, zips the flap just like they’re on a camping holiday and sits or lies there and waits.
The reduced oxygen levels don’t make it easy. In Paul Kimmage’s book “Rough Ride” the Irishman recounts how he struggled to sleep after a mountain stage when staying at altitude. But if some find sleeping in a ski resort hard, try to imagine being even higher and then inside what amounts to a large unbreathable plastic bag and add the noise of the pump rumbling nearby.
Who Uses It?
There’s hardly a central register but usage is very common. The old Slipstream-Chipotle jersey even used to feature the CAT logo, a provider of this gear.
Sleeping in my tent tonight after nearly a kilo of wife’s beetroot soup, you know what comes next
— Bradley Wiggins (@bradwiggins) June 14, 2012
I don’t think Wiggins was on a camping holiday. This isn’t to single him out, I recall it mentioned for Cadel Evans and many riders do the same. In recent days, I’ve seen a piece in Cyclesport Magazine where Thomas de Gendt is mentioned. And I got the idea for this subject after a tweet by Greg Henderson yesterday:
— Greg Henderson (@Greghenderson1) June 18, 2012
The Mile High Club?
Typically riders train at sea level and then climb into this at home to rest or even sleep overnight. But as Wiggins hints above when a kilo of beetroot soup meets intestinal bacteria the results in a near-airtight chamber must be horrific. A tent isn’t the most romantic place at the best of times, yet alone an airtight one with a noisy pump standing outside. Add this to the actual altitude where the reduced oxygen levels get uncomfortable and it’s no wonder riders tend to rig these in the spare room or basement as opposed to the marital bedroom.
But at least this allows the athlete to stay at home. Sleeping at altitude for real means staying in a remote ski resort out of season which can be peaceful but it means staying in a cold place where snow can be common and a long drive awaits to find flat roads.
In one word: legal. But if it’s legal in most countries it is not allowed in Italy where a rule forbids manipulation of blood values via artificial means.
This is a tricky subject because it uses artifice to trigger a response in the body instead of going to altitude for real. For me a crucial difference is that this uses an exogenous method to trigger the response as opposed to an endogenous means like swallowing a pill or injecting EPO. In addition whilst some have gone wild with EPO it is hard to make the body respond to hypoxia, the gains are far slower and more limited. Organisations have looked at banning this method but there are practical difficulties. Short of raiding someone’s house it is impossible to detect.
Sometimes called an altitude tent a “hypoxic chamber” would be the more appropriate term. These rely on pumps normally designed for the sick but modified to provide reduced oxygen to the athlete.
It’s legal but relies on artificial and technological means to make the body adapt. But some users don’t respond well to hypoxia and the performance gains can be limited for those that do. But in a competitive environment where the smallest legal gains are seized it is understandable that the use of these machines is a widespread but often unspoken part of the training regime.