The higher you go, the ‘thinner’ the air becomes. The reduction in air pressure leads to less air resistance, so athletes who sprint, jump and cycle often perform better at high altitude venues. For endurance events, this lack of air pressure becomes a significant issue, as it leads to less oxygen in the blood stream, which impact upon aerobic performance.
What is air pressure?
Air pressure is measured as mm Hg (millimetres of mercury), if you’ve got one of those weather things at home or in the garden, you’ll often see ‘mm Hg’ on the scale. Standard air pressure at sea level is 760 mm Hg, that’s how much resistance you have to overcome when you run or ride your bike. At an altitude of 1344m (the height of Ben Nevis) the air pressure is lower at 650 mm Hg. Cyclists who have completed the hour record (how far you can ride on a track in a single hour) have historically completed the challenge at altitude. More recently, the Olympic Velodrome manipulated the climate conditions inside the building in an attempt to reduce air resistance and increase the likelihood of world records. Air pressure can be simply described as the ‘air density’. If you’re trying to ride through dense air, it’s like riding through water. If the air is thin, you slice through with less resistance. Time trial cyclists will know the importance of weather conditions, they know instinctively that following a big storm, the air is just right for personal bests!
I thought it was harder to compete at altitude for endurance athletes?
Physiologically speaking, yes, it is harder for athletes to compete at altitude. This would certainly be the case for most endurance sports. The hour record is slightly different as the benefits in aerodynamics and reduced air pressure, can outweigh the physiological disadvantage of less oxygen reaching the muscles. For long distance runners, competing at altitude would not be beneficial in any way!
Why does less oxygen get to the muscles?
Air pressure flows from high to low, consider the following example: The pressure in your bike tyre is higher than the surrounding air pressure. When you press the valve the air will therefore flow OUT, from HIGH to LOW. The air will continue to leave your tyre until the pressure inside the tyre matches the pressure in the outside air, then it stops flowing. When you inflate your tyre, your bike pump compresses the air by pushing down the handle. This leads to high pressure inside the pump (higher than the pressure inside the tyre), so the air flows into the tyre, from HIGH to LOW.
How does it work for humans?
When your lungs expand, the air pressure inside them drops lower than the outside air pressure. By opening your mouth, you allow the air to flow inwards (from HIGH to LOW). When you compress your lungs, this squashes the air inside them, raising the pressure so it’s higher than outside air pressure. The air therefore flows out of your mouth. We said earlier that air pressure is lower at altitude. When you expand your lungs and open your mouth to let air in, you presume that the pressure in the outside air in higher than it is in your lungs (so air will flow from HIGH to LOW into your lungs). What happens if the outside air pressure is also low? You open your mouth, the air pressure in your lungs is low and the outside air pressure is also low… air flows nowhere! Much of the talk about altitude generally refers to the ‘lack of oxygen’ when in fact the real reason that oxygen supply to the muscles is reduced, is the lack of air pressure.
What happens when you train at altitude?
The reduction of oxygen in the blood stimulates the release of erythropoietin (EPO) and this results in an increase in haemoglobin and red blood cells. This is the body’s way to deal with the lack of oxygen in the blood stream. Endurance athletes will often spend periods of time at altitude to boost their red blood cell levels, in the hope that when they return to sea level, their performances will be improved. One of the most significant issues relating to training at altitude is the inability to maintain both volume and intensity of normal training. In simple terms, you can’t train hard when you’re at altitude. To resolve this problem, athletes will follow a ‘HILO’ approach, which means they live HI and then train LOW. They will live at high altitude and then drop down to sea level when they need to train, so their workouts are not affected. The biggest problem relating to the HILO approach is the geographical limitations. Firstly, athletes must travel to a part of the world where they can sleep at altitudes of 2200-2500m. Secondly, they must then deal with the practicalities of training at ‘sea level’. This may require living and sleeping at a ski resort, whilst driving to lower altitudes to carry out training sessions.
There is an easier way
This geographical problem has largely been removed by the access to hypoxic or hypobaric chambers, thereby allowing athletes to remain at home in many cases whilst still benefiting from the HILO approach. Hypoxic chambers transform a normal room or building into a hypoxic environment. Athletes are now able to purchase a simple tent, which can be erected over their bed and with the use of a simple device, they can replicate altitudes of 2200-2500m whilst they sleep. Some training facilities have gone further and established training houses with dormitories where athletes are continually residing in hypoxic conditions to match 2200-2500m.
What’s the difference between hypoxic and hypobaric?
The word hypobaric, means ‘low pressure’. We mentioned earlier that air pressure drops when you are at altitude. The simple tent structures that you place over your bed, as used by the Brownlees and other elite athletes are not hypobaric. The air pressure in those tents is the same as general sea level, instead, they reduce the amount of oxygen in the air (swap it for nitrogen). They are therefore ‘hypoxic’ (low oxygen) but not ‘hypobaric’ (low air pressure). Hypoxic devices are much more easily available and have the same desired effect, i.e. generating red blood cells.
Applying Hypoxic Training
There are 3 ways of using hypoxia. The first is to sleep or live for longer periods of time in a hypoxic environment. This may be as simple as erecting a tent over your bed and sleeping 8-10 hours inside. The most common recommended altitude is 2000-2500m, this is moderate altitude.
The second option is termed IHT (Intermittent Hypoxic Therapy). This is based upon short exposure (60-90 min per day or less), at significantly higher relative altitudes (6000m+). This option is generally done passively, sitting in a chair whilst holding a mask over your face and breathing hypoxic air. In simple terms, this is a ‘much harder hit for a shorter period of time’.
There is a third option, to consider as both of the above do not involve exercise. You could exercise on a treadmill or indoor bike, whilst wearing a mask and breathing hypoxic air. If you are exercising, rather than sitting still, then the recommended altitude would be similar to option 1 (2000-2500m).
I’m feeling a bit light headed after all this talk of altitude, so we’ll stop here for now. Next week, we’ll look at what out there on the market and how it can be used to enhance your general performance. How can you apply altitude training in your everyday life and what’s the potential benefits to performance?
If you found this article useful, it would help us a great deal if you share on Facebook, Twitter and social media.
Until then, stay low and fast
Sports Science lecturer for 10 years at St Helens HE College.
2004 established The Endurance Coach LTD sports science and coaching business. Worked with British Cycling as physiology support 2008-2008. Previous Triathlon England Regional Academy Head Coach, North West.
In 2006 established Epic Events Management LTD. Now one of the largest event companies in the NW, organising a range of triathlon, swimming and cycling events. EPIC EVENTS also encompasses Montane Trail 26 and Petzl Night Runner events.
In 2010 established Montane Lakeland 50 & 100 LTD. This has now become the UKs leading ultra distance trail running event.
In 2010 established The Endurance Store triathlon, trail running and open water swimming store. Based in Appley Bridge, Wigan, we are the North West’s community store, organising and supporting local athletes and local events.
Check out the endurance store HERE