06 May 2008
POWERbreathe… at high altitude
Tasks that would normally be a ‘breeze’ at sea level, suddenly leave you gasping for breath and wondering where all your fitness has gone. The explanation for the symptoms is simple, but not always well understood.
At high altitude the air is ‘thinner’, containing less oxygen than at sea level. The higher we go, the thinner it gets. The effect of this is to make your breathing work harder to get the oxygen into your blood stream. For a given level of oxygen demand, you may need to breathe three, four, or even ten (at very high altitude) times as hard. At 3km (3000m) the amount of oxygen in the air decreases by 30%, and at 5km its half that at sealevel. This means that at around 1km you begin to experience breathlessness during moderate exercise, and at 4km you feel breathless at rest.
Just to put things into perspective: whilst resting at sea level, you breathe about 12 litres of air in and out of your lungs each minute. At the summit of Mt. Everest (8848m) it requires almost maximal levels of breathing (in excess of 150 litres per minute) just to put one foot before the other. This level of breathing can be sustained for only a couple of minutes at a time. At sea level, your ability to exercise is limited by the capacity of your heart to pump blood to the exercising muscles. At high altitude, you become limited by the ability to pump air in and out of your lungs, and this is determined by how ‘fit’ your breathing muscles are.
Climbing, hiking, or skiing at high altitude place enormous demands upon the
breathing muscles. Instead of needing to provide, say, 20 litres per minute of air in and out of your lungs to walk at a moderate pace up hill, they may need to increase this to 60. This increased work of breathing has a number of consequences, the first of which is to make the exercise you’re doing feel much harder than it would normally.
Human beings tend to ‘learn’ from experience what is an appropriate level of breathing for a given exercise task. When there is a mismatch between your previous experience and your current experience (as occurs at high altitude), you get a heightened sensation of breathlessness, which we interpret as an increase in the intensity of the exercise. Also, if your respiratory muscles are working very hard, they can ‘steal’ blood from the legs to meet their own requirement for oxygen. This can impair your leg performance, and make the effort of walking or skiing much greater. Finally, the increased work of breathing can lead to chronic fatigue of your breathing muscles, which also increases breathlessness and impairs performance.
Research has shown that well-trained mountaineers experienced a smaller increase in their sense of effort at high altitude if they trained with POWERbreathe before the expedition (Romer et al., 2000). They also experienced a smaller decrease in the strength of their breathing muscles at high altitude, which remained stronger than the mountaineers who did not use POWERbreathe. Since the strength of the muscles determines how easily they become fatigued (McConnell et al., 1999), and POWERbreathe training also reduces inspiratory muscle fatigue (Volianitis et al., 2001; Romer et al., 2002), POWERbreathe training offers protection from breathing fatigue.
By training with POWERbreathe prior to trekking / climbing at high altitude, or a skiing trip, you can prepare your breathing for the rigours of the increased work of breathing, minimise fatigue and breathlessness, and improve performance and enjoyment. Short of spending a few weeks doing lots of aerobic exercise at 3000m, there’s not much else to rival POWERbreathe’s ability to get your breathing prepared for the mountains! Whether its an assault on K2, or a skiing trip to the French Alps, training your breathing for just four weeks before you go could help you to reach new heights of enjoyment and achievement.
POWERbreathe has been used on two separate expeditions to high altitude; once in a study done by Lee (Mount Kachenjuga - 1998 - the J. Physiol abstract), and once to Kilimanjaro in 2003 (Gary Devis is currently analysing the data on this and writing it up). Both studies found that altitude impaired inspiratory muscle function, and that this was alleviated by training with POWERbreathe before the trip. Once at altitude, the POWERbreathe users experienced smaller increases in effort perception than the control group.