Wednesday, June 12, 2002 - Physiology
Dispelling Some Altitude and Training Myths

- By: Dr. Donald Christie Jr.

At first blush, living and training at altitude seems the ideal way to "naturally" acquire the extra oxygen-carrying red blood cell capacity needed to compensate for competing at altitude (our predicament at Soldier Hollow, as we had discovered -- "big time" -- in Mexico City years before), as well as bolstering endurance performance at sea level. Should we be surprised, however, that it's not that simple? The Devil's in the details.

At the risk of shedding more darkness than light on this, I offer the following "details."

If all we had to do was "naturally"' boost our red cell mass once and forever, then the increases in performance "proven" by controlled experiments might be hunky-dory. We live in a real world, however, a world in which we fly here and there to compete, then home (or wherever) to train, before rushing off to the next venue, a real world of a sport in which the majority of our training is on "dry" land, not ice crystals. Unless we have the wherewithal to cart around our altitude room (and the sanity to remain inside it for at least 12-15 hours a day when we aren't living in the high mountains), this seesaw exposure to low and high oxygen tensions sends very mixed signals to our kidney tubules, which turn erythropoietin (EPO) synthesis on or off. (Tongue in cheek: Of course, one could adopt the solution of some European cyclists and Nordic skiers: take injections of erythropoietin or darbepoetin and save all that trouble!)

The real world does not present the standardized and controlled conditions of the laboratory. In fact, authors of those "live high, train low" studies admit methodological problems, and the results were anything but "clean" and clear. Earlier experiments, simply showing improved endurance capacity with increased red cell mass, were typically done on cyclists in laboratory settings and were really one-time demonstrations of the effect of that single intervention. They didn't study what happened to EPO levels and red cell survival as oxygen tension (in effect, altitude) varied over time, as it does in the real world of high-level competition.

Some of the "noise" in the "live high, train low" experimental results derives from the difficulties of conducting an experiment involving human subjects engaged in real-life training and competition and the hard-to-control variables. One study done with runners involved high mountain living (cool, dry air) for a month or more, with training conducted at a somewhat lower altitude, followed by descent to sea level (hot and humid). At first, there was a DROP-OFF in performance, with no evidence for a gain (over their performance before going to altitude) until they had been back at sea level for 2-3 weeks. The authors attributed this to the need to adapt to heat stress. While they tried to measure actual red cell mass (to control for changes in plasma volume with ascent, descent, and hydration status), they may have failed to detect an up-until-recently unexplained rapid LOSS of red cells with fluctuations in EPO level.

From the space program, of all places, we have had a glimpse into what may be happening to our red cells with "living high," then "going low," here on Earth. (This past season's Alaska, Ontario, and Wisconsin venues were basically "low.") NASA was curious about why astronauts became anemic in space, and had discovered that it was due partly to what happens to one's blood volume in microgravity. It mostly contracts to the body's core -- no gravity drawing it out to the extremities -- and is thus sensed to be excessive (remember that spaceships are pressurized, so there is no low-oxygen stimulus to EPO production) and EPO production is halted. The now-sensed "excess" volume of fluid within the blood vessels is quickly eliminated through a brisk diuresis. (Ask astronauts how much extra they urinate during the first 24 hours in space!) However, NASA scientists discovered that there was a rapid drop in the newly concentrated red cells, a faster and disproportionately greater drop than any shutdown of marrow red cell production could have explained. (Marrow red cell production does not fully "turn off" for several days after a decrease in EPO.)

It appears that this abrupt red cell loss is due to the breaking apart (hemolysis) of the most newly minted red cells. NASA-sponsored studies of Peruvian Andes natives before and after they flew down to sea level, indicated that the decreased EPO, a result of the sudden descent to sea level and the body's sensing that it now had WAY more than enough oxygen-carrying capacity, in addition to eventually letting the marrow's red cell production shut down, allowed the newest red cells to break apart. This resulted in a drop of almost 10% in red cells within the first week at sea level! (In a couple subjects, the results were not as clear-cut, but when the study codes were broken and subjects identified, they turned out to be individuals who had gone back up to their mountain home, then back down to Lima, within a short period of time, hence signaling the EPO "off" and "on" switches. Control subjects were given EPO injections before and after descent and -- sure enough -- experienced no such loss of red cells once at sea level.)

What might all this mean for skiers? First, we need to look at the "live high, train lower" data in a new light, i.e., what happens to all those boosted red cell masses when athletes move from "high" to "low"? Second, we need to emphasize the value of living and training low: One simply can't "push the envelope" in above-threshold or near-threshold training in rarified air as one can at sea level. We need to see the likely folly of "naturally" fooling Mother Nature into making more red cells than we really need. One may be competing at elevated venues one week, then go down at near sea level for a couple weeks, then back to altitude for another week, etc. Such about-faces in the signal for EPO secretion and the emerging understanding of the role of EPO, not only as a marrow stimulant, but as a factor allowing new red cell survival, tell us that those that try to get in bursts of living high, but then train or compete "low," may be too clever by half.

You might ask, why not "live high" and "train high," using supplemental oxygen to allow high quality training at altitude? Indeed, athletes have tried this, but the extra weight of the oxygen tank negates the benefit. If a light-weight mask and tube extending to the O2 tanks are used for high-quality training sessions, one then can perform the experiment -- except that it is really not "real world," and one cannot recruit serious athletes to spend hours of their time, encumbered by a tight-fitting mask while working out on a treadmill or stationary cycle, for what may turn out to be a "bust" -- not unless they really need the pocket money!

The "long and the short of it": Quality training at sea level is looking better than ever! Even those who can afford the money and stand the hassle of trucking around their altitude room may get wind of the strange effect that fluctuating oxygen tensions and changing EPO levels will have on their actual red cell numbers. Our attention should be refocused on patient, comprehensive development of gifted adolescents and young adults, respectful of the need for time as well as technique and not looking to artificial physiologic "fixes" and "fudges" to rescue us from poorly conceived and impatiently executed programs.

Dr.Christie graduated from the University of Rochester medical school in 1968 and received specialty training in internal medicine from the University of Iowa. He became a member of the American College of Sports Medicine in 1976, participated in an ad hoc study group that defined "sports medicine" and "team physician" in the late '70's, and was later elected to Fellowship in the College. He has served as varsity team physician at Princeton University for six years. For the past year, he has been devoting all of his practice time (and much of his "off-duty" time) to sports medicine and exercise science, with a particular concentration on Nordic skiing.

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