Saturday, July 13, 2024
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The Party of the Big Tent

Altitude training has for some years now been widely practiced in the upper echelons of sport, and has developed a considerable interest in the scientific community. There are scholarly papers published in peer-reviewed journals, and even international conferences.  Uncontrolled, anecdotal studies date back to the early 1960’s ( e.g., Saltin, 1967 )  and controlled studies appear to have been pioneered  by Adams et al., 1975.  Ironically, the Saltin study reported a decline in the performances of  7 of his 9 subjects,  all describe as ‘elite athletes’ in a variety of sports.

The basic idea is simple: training in the hypoxic conditions of high altitude, real or simulated, is thought to induce performance-enhancing adaptations in activities wherein performance is closely correlated with oxygen exploitation.  Put the athlete in an environment where oxygen is scarce, and his body will adapt, becoming more efficient at exploiting what oxygen is available. Then, when you set the athlete to compete in a sea-level, or normoxic environment, he’s supercharged by his altitude adaptations.

For a while, the practice of ‘blood-doping’ made headlines when it came to light that Olympic athletes were training at high altitudes, thus raising their RBC counts and hemoglobin, drawing their own blood, storing it and then re-infusing it into their own bodies just before the low-altitude competition. Seemed sort of kosher: no steroids, no hormones of the sort that produced East German womens teams consisting of Arnold Shwarzenegger clones, and it seemed to work. Seemed to work so well, in fact, that the US Cycling team got the brilliant notion to give it a try at the 1984 Olympics. Only trouble was, their logistical plan didn’t allow for a period of altitude training during which to sex up the team members’ red-bloodedness. Not to be deterred, somebody came up with the ingenious idea of buying some nice hi-octane juice from high-altitude relatives, friends and frank strangers with matching blood types. It worked ! The team brought home a record 9 gold medals. Oh, yes, and a similar number of hepatitis cases.

Blood doping , for a variety of unwholesome reasons, is now a thing of the past,  but, nobody any longer seriously doubts the effectiveness of altitude training in the O2  intensive sports. There is some controversy along the fault line separating the Live Low/Train High camp and the Live High/Train Low faction, and the puzzle of the pioneering but counterintuitive Saltin study seems to have been solved.


Timing has a lot to do with it. If you take your athlete up from her luxurious seaside crib to a high Sierra training facility, the first thing that’s going to happen to her is she’s going to feel like crap when she tries to work out. Her regular sea-level workout ? Dream on. She’ll have to begin her altitude adaptation slowly and incrementally, and gradually build back up toward the performances levels of her sea level regimen.  Thus, her general level of fitness is likely to decline, rather than increase during the first, early stages of adaptation to altitude. Her relatively low levels of activity may result in loss of muscle mass and other decrements in those fitness parameters most sensitive to reduced activity: the so-called “detraining effect”.  A plausible explanation, then,   for Saltin’s weird finding that altitude training harms athletic performance is, then , that Saltin’s athletes were returned to sea level and re-tested at far too early a stage in their adaptation to altitude. No wonder they performed worse than their benchmark measures !

And the march of technology continues. The air tickets between Florida and the Colorado Rockies have been replaced by a device which simulates high altitudes in the comfort of your own home: the hypoxic tent. 

Simply put, the hypoxic tent is a closed environment in which the composition of the air can be controlled to reduce the oxygen content.   You spend time in a reduced-oxygen environment ( although in most cases, at sea-level pressure) and reap the benefits of living high, while continuing your sea-level training regimen at full intensity.

The most obvious impact on physiological variables are increases in EPO, the hormone that stimulates red blood cell production,  and the cascade from this increase to increased red blood cell counts and increased HCT (hematocrit), i.e., the proportion of your blood consisting of red blood cells.

For the physiologically challenged,  though I doubt any such are to be found among our Readership, it is those lovely red blood cells that carry precious hemoglobin, the substance that bonds with oxygen and delivers it to each and every cell in the body. Our own internal Federal Express of O2.

In contrast to previous methods of blood enrichment, the hypoxic tent is relatively free of  nasty side effects such as the hepatitis epidemic among the 1984 US Olympic cyclists, or the bankrupting effects of constant travel between high-altitude and low. There is evidence, too, that the pressure differences between actual high and low altitudes constitute a complicating factor which may not have entirely benign effects.


As with any training technique, technology or hot sauce, a determined obsessive can, indeed, harm herself with her hypoxic tent. Humanity’s ability to walk into telephone poles is, apparently, a genetic endowment from our Neanderthal past.  There are people who take it for granted that if a little of something is good, then more is always better. In the 1980’s, for example, several Dutch cyclists managed to kill themselves by pushing altitude training to the point where  absurdly high EPO levels and hematocrit in excess of 70% made it impossible for a system and a pump designed to move a liquid around to function. Their blood was not really liquid any more, so they were very vulnerable to stroke, heart and lung failure. At 70% HCT, I would suppose their blood was the consistency of WD50 motor oil. All that to win a bicycle race.

But what of freediving ?  If ever there were a sport that  invited the use of hypoxic tents, this would seem to be it. We don’t need to train efficient breathing – we need to train no breathing. The cyclists, runners, skiers, mountaineers, and other endurance athletes have been bedding down in their hypoxic tents for years, and to good effect. Some champions and trainers in these sports take it for granted that an athlete who does not exploit this technology can no longer be considered a serious contender.

Hypoxic tents are becoming a part of the freediving scene, at the high-end, world champion level. There is every reason to expect that before long, they will become de rigeur at the championship level and popular among well-heeled recreational freedivers.

The next two installments in this series will get into the lowdown on hypoxic tents and freedivers, naming names, discussing training philosophies and reviewing several manufacturers’ offerings. So as not to ruin your evening, we won’t mention prices here: suffice to say these are not cheap toys. 

Paul Kotik
Paul Kotik
Paul Kotik has been a Staff Writer and Freediving Editor for He lives in Florida, USA with his family.