Q+A: What are the effects of altitude training?

Q I understand that haemoglobin levels increase following a stay at altitude. I am soon off to the Alps for a couple of months and wonder how my training will be affected. Will it make my blood thicken, potentially leading to heart attacks? I know cyclists who take synthesised erythropoietin (EPO) have suffered from this, but I’ve also heard that people who live at altitude are healthier. What’s going on?

A Red blood cells carry oxygen from the lungs to the muscles to maintain aerobic work. The more oxygen delivered, the better. Altitude training triggers the kidneys to release more EPO, stimulating the production of red cells, and hence increasing the delivery of oxygen. Altitude training may be beneficial for some (but not all) athletes, giving perhaps a one to two per cent increase in endurance performance, which may make a small difference in race results. Not all athletes benefit equally; some respond to altitude training, while some don’t.

With altitude training at around 2,000-2,400 metres, the percentage of red cells may rise to just below 50 per cent (normal levels are approximately 40-50 per cent in men and 37-47 per cent in women). At this level one would not expect any “thickening of the blood” leading to heart attacks. However, athletes taking EPO as a doping agent are often looking for higher levels of red cells, so the difference could be one of quantity.

When cardiologists talk of “thickening of the blood”, they usually mean thickening with fats and the clotting material fibrinogen, rather than extra red cells. Some scientists believe training at moderate altitudes (2,000-2,300m) may be detrimental to general health, raising levels of damaging free radicals, and depressing the immune system, but these are not because of raised levels of red cells.

However, most agree that training or living at modest altitudes (2,000-2,300m) is unlikely to harm you, and it may well help your performance.

Professor Craig Sharp, exercise physiologist, Brunel University