Even small improvements in performance often take hours of training, hours which for the recreationally competitive athlete are often difficult to find when they have to juggle family life, work and training. One of the most overlooked adjuncts to training that has continually shown performance benefits is intermittent hypoxic training. Intermittent hypoxic training (IHT) makes use of a machine that decreases the amount of oxygen that you breathe, simulating altitude. IHT training has been shown to increase power at both anaerobic threshold and VO2 max by 4-6% in as little as three weeks with daily use of IHT for an hour at a time. This is about the equivalent of six months or more of improvements from actual training for most age group athletes. The real advantage to IHT training is that it is a passive form of training, you sit there attached to the machine and breathe while reading, watching TV or responding to e-mail.
How Does it Work?
Hypoxia, a decrease in the oxygen content of the air you are breathing stimulates the release of erythropoietin, the hormone responsible for producing red blood cell. With repeated exposure you will gradually increase the total number of circulating red cells and the oxygen carrying capacity of your blood.
Many people mistakenly believe that the use of hematocrit, the cell component of blood, levels are a good indicator of whether the IHT is working or not. If you were to take hematocrit measures every day while using IHT you would likely see an increase in hematocrit for a short time and then a gradual decrease back to normal levels as blood volume increases. If you only take a hematocrit reading at the beginning, middle and end of the IHT program you are unlikely to see any changes.
The human body likes to maintain hematocrit within a relatively narrow range, normal variations in hematocrit are typically less than 4% over the course of a year. One of the primary adaptations to aerobic training is an increase in blood volume, resulting in a decrease in hematocrit levels, reducing blood viscosity and resistance to blood flow, and improving cardiac output. There is a strong positive correlation between blood volume and endurance performance but contrary to what many athletes believe there is a negative correlation between hematocrit and performance. In other words high hematocrit levels actually decrease aerobic capacity. A lower hematocrit keeps blood viscosity lower and improves blood flow rate which improves oxygen transportation and transfer of oxygen to the muscles.
Given the amount of time and effort that you put into your training, the investment in IHT training is well worth the possibility of doubling the amount of improvement most people typically see in a year.
Thirup, P. (2003). Hematocrit: Within subject and seasonal variation. Sports Medicine. 33(3) pp 231-243.
El syaed, M., Ali, N., and El sayed -Ali, Z. (2005). Haemorohlogy in exercise and training. Sports Medicine. 35(8) pp 649-670.