By Matt Fitzgerald
For Active.com Oxygen is as important to running performance as it is to life. One of the physiological characteristics that all great runners share is a high aerobic capacity, which is a fancy way of saying a huge capacity to suck oxygen from the air and deliver it to their muscles, which use oxygen to release energy.

And one of the surest ways to improve your running is to increase your aerobic capacity. Some newer high-tech gadgets actually help you do this without running a single extra step.

Altitude Tents

Altitude tents are among these devices. As their name suggests, these tents simulate high altitude either by reducing air pressure or by reducing the oxygen content of the air inside them.

Whenever you spend time in an environment with unusually low oxygen content, your body responds by creating more red blood cells, which carry oxygen through the bloodstream. The result is a higher aerobic capacity and the ability to race faster in normal air.

Most altitude tents are designed to be slept in, as research has shown that athletes need to spend at least eight hours a day "at altitude" to experience significant benefits. Two of the leading manufacturers of altitude tents are Hypoxico (www.hypoxictent.com) and Colorado Altitude Training (www.altitudetraining.com). The tents typically cost $7,000 to $10,000.

If money is no object, both of these companies and others can also convert your entire bedroom (or any other room) into a hypoxic chamber. This will probably cost $12,000 to $18,000 and, if used properly (that is, according to the detailed instructions provided by the manufacturer), will lower your PRs by two to four percent.

Intermittent Hypoxic Training

Fortunately, a slightly cheaper and far more practical alternative is emerging: intermittent hypoxic training (IHT). This method is based on the discovery that the stress of adjusting to changes in "altitude" is a stronger stimulus of the desired adaptations in oxygen transport than cumulative time spent at "altitude."

The favored protocol that has emerged from testing with athletes is a series of five-minute exposures to oxygen-poor air (roughly 10 percent oxygen) separated by breaks of equal length. Instead of entering a hypoxic chamber, athletes simply breathe through a mask attached to a portable machine.

Research suggests that athletes can improve aerobic capacity and performance as much through 60 minutes a day of IHT as they can through eight hours of sleep in a hypoxic tent or room. The leading manufacturers of IHT units are Hypoxico and Go2Altitude, an Australian company. Recently their prices have come down sharply, but the units still cost several hundred dollars.