Posted: July 15, 2005

Science of Sport: Do Runners And Cyclists Have To Worry About EIAH?

By Owen Anderson, Ph. D. (Copyright © 2004-2005)

Well-trained endurance athletes have a problem which moderately trained sportspersons usually do not have: When they exercise at very high intensities – just when they need oxygen the most – their blood becomes unsaturated with oxygen, i. e., the hemoglobin in their red blood cells begins carrying around less oxygen, instead of more (1). This somewhat-surprising reduction in the quantity of oxygen carried by the blood is called exercise-induced arterial hypoxemia (EIAH). As you might expect, EIAH can have a negative effect on VO2max, and it can also limit the performance capacity of highly trained endurance athletes (2).

Strangely enough, some studies have suggested that EIAH is a bigger problem for runners, compared with cyclists (3). Is this really the case? Can runners train in ways which might limit the negative effects of EIAH?

To find out, Paul B. Laursen from Edith Cowen University and the University of Ballarat in Australia and his colleagues from the University of British Columbia in Canada recently studied 13 very fit male triathletes (4). The subjects had an average VO2max of about 65 ml kg-1 min-1, and they trained approximately 17 hours per week (three hours of swimming, nine hours of cycling, and five hours of running). Average age was 36, and body-fat percentage was 12 percent. All of the athletes performed progressive tests to exhaustion while exercising on a cycle ergometer and also while running on a treadmill, in random order. For the cycling test, the triathletes started at an intensity of 100 Watts and bumped their power upward by 30 Watts every minute until they were too fatigued to continue. In the treadmill exertion, the participants started at a running speed of 5.6 kilometers per hour (an easy tempo of about 17 minutes per mile) and increased running pace by .8 kilometers per hour each minute until a velocity of 16 kilometers per hour (about six minutes per mile) was reached. At that point, the treadmill grade was elevated by 2 percent each minute until the athletes fell prostrate on the laboratory floor.

Generally, an endurance-runner’s VO2max will be higher during running, compared with cycling, while an endurance-cyclist’s VO2max will be superior during biking. These were triathletes under study, however, and they managed to achieve similar maximal rates of oxygen consumption while running and riding. Somewhat contrary to expectation, the degree to which blood hemoglobin was saturated with oxygen decreased over time during both the cycling and running tests, i. e., the athletes suffered from EIAH during the cycling effort, as well as during the running blast-off. Previous studies which linked EIAH more tightly with running than with cycling may have been carried out with individuals who were less-experienced cyclists – and thus who were less able to sustain high-enough intensities on the bike to provoke EIAH.

Some studies have suggested that a relative hypoventilation is a key cause of EIAH in well-trained athletes, i. e., such competitors may simply not be breathing in oxygen at high-enough rates to keep the blood supplied with the precious gas (5). The basic idea is that top-level athletes have the capacity to breathe at higher rates, but appropriate physiological processes do not induce them to do so during top-end efforts. In line with this, one piece of research was able to show that as ventilation rates were reduced in athletes engaged in stair climbing, oxygen saturation of the blood was significantly decreased (6). This seems sensible enough, and anecdotally many runners do seem to have trouble maintaining high rates of breathing. One problem with this theory, however, is that elite runners, the ones most prone to EIAH, are generally good ventilators. In addition, Laursen and his crew found no link between oxygen saturation and ventilation rate; the athletes who ventilated air at the greatest rates seemed to develop EIAH as frequently as the less-wealthy ventilators. The actual cause of EIAH remains unknown.

What is know, however, is that certain types of training seem to put an athlete at less risk of developing EIAH (7). So, how should you train in ways which will reduce your chances of suffering from EIAH – just when you are about to set a 5-K PR?

It’s useless trying to set up a training schedule which will promote adaptations by your lungs. The lungs are stolid structures, impervious to training, and they won’t grow new air sacs for oxygen exchange between inhaled gas and the blood, no matter how many sizzling workouts you conduct.

Working on your respiratory muscles (by using a special breathing device, for example, which increases the resistance encountered by air flowing into the lungs and therefore strengthens the diaphragm and intercostal muscles) is unlikely to be helpful for this specific problem. Such respiratory-muscle training might improve ventilation rate, but remember that ventilation-rate deficiency does not seem to be the prime source of EIAH. Respiratory-muscle workouts are probably helpful in reducing respiratory muscle fatigue during strenuous and prolonged exercise, which lessens an athlete’s overall sense of fatigue and thereby may heighten performance capacity, but they shouldn’t eliminate the possibility of hurtful EIAH.

There is another approach, however, and it involves accepting the fact that EIAH is probably going to occur during sustained, high-intensity running - and then training in a way which limits EIAH’s performance-thwarting impact on the muscles. As Paul Laursen points out, when EIAH occurs during high-intensity running, leg muscles are forced to rely more heavily on anaerobic metabolism to meet the energy demand of the fiery striding. This creates a situation in which hydrogen-ion concentrations can increase dramatically inside the muscle cells, making the intramuscular milieu much-more acidic than usual. Such acidic conditions have been linked with high levels of muscular fatigue. The muscles’ best “answer” to these vinegary swings is to develop a variety of different “buffering” systems which sop up the hydrogen ions and create seas of tranquility within the muscle cells.

You probably do not want me to delve into the esoterica of the various muscle-fiber buffering systems, and so I won’t. What you would probably like is a workout which forces your muscle cells to wake up and begin burgeoning their buffering in dramatic fashion. Here it is:

(1) Warm up with a combination of easy jogging and dynamic-mobility drills until you feel relaxed, loose, and ready to run very fast.
(2) Run at all-out intensity for 90 seconds. Stay very relaxed as you do this; please don’t strain, and don’t let your legs or upper body “tighten up.” Simply unleash all of the power in your legs in a rhythmic, coordinated way. Keep your arms loose and in-synch with your legs, and keep your neck and facial muscles relaxed.
(3) Jog easily for 150 seconds to recover.
(4) Repeats steps 2 & 3 five more times (for a total of six 90-second “blasts” in all).
(5) Cool down with two miles of easy running.

After the sixth 90-second repeat (and actually even more so during the recovery from this repeat), your muscle-cell interiors will be seething gulfs of hydrogen ions. Your muscle cells will respond by shoring up their hydrogen-ion buffering protocols. If you carry out this workout consistently, your buffering capacity will continue to improve, you will be better able to withstand EIAH, and you will handle the furious closings of your 5-K and 10-K races much more successfully.

Progress with this workout by slowly building up to 10 90-second blast-offs per session. Note that this will mean that you are “taking off” for 90 seconds every four minutes during the “meat” of your workout, and that the 10 reps and recoveries will require a total of 40 minutes, a relatively low “time price” to pay for the ability to withstand the kind of hard running which produces EIAH. During your racing season, you will want to carry out a workout such as this one approximately once every two weeks. Note that it is a training session which can enhance maximal running speed and lactate-threshold velocity, in addition to its positive effect on buffering.

This session works best on soft, smooth ground (preferably a trail, a not-too-well-packed dirt road, or short, even grass), especially when you are carrying it out for the first few times. If you are trying to run on concrete or asphalt, the very fast running can give your legs the kind of pounding with which they are not especially familiar (always remember that there is a direct relationship between running velocity and impact forces).

There is good scientific support for the idea that the kind of intense training carried out in this workout enhances muscular buffering capacity (8). The innovative Laursen is currently carrying out research which looks at the effects of very high-intensity training on the muscle cells of rats (it is a bit easier to obtain muscle biopsies from them, compared with well-trained athletes who hate to see too many of their muscle fibers placed under the microscope or used for histochemical analysis). ©

References

(1) “Incidence of Exercise Induced Hypoxemia in Elite Endurance Athletes at Sea Level,” European Journal of Applied Physiology and Occupational Physiology, Vol. 58, pp. 298-302, 1988
(2) “Effects of Incomplete Pulmonary Gas Exchange on VO2max,” Journal of Applied Physiology, Vol. 66, pp. 2491-2495, 1989
(3) “Pulmonary Gas Exchange during Exercise in Women: Effects of Exercise Type and Work Increment,” Journal of Applied Physiology, Vol. 89, pp. 721-730, 2000
(4) “Exercise-Induced Arterial Hypoxemia Is Not Different during Cycling and Running in Triathletes,” Scandinavian Journal of Medicine & Science in Sports, In Press, 2004
(5) “Exercise-Induced Arterial Hypoxemia,” Journal of Applied Physiology, Vol. 87, pp. 1997-2006, 1999
(6) “A Comparison of Exercise Responses in Stairclimbing and Cycling,” Journal of Applied Physiology, Vol. 46, pp. 510-516, 1979
(7) “Exercise-Induced Hypoxaemia in Highly Trained Cyclists at 40% Peak Oxygen Uptake,” European Journal of Applied Physiology and Occupational Physiology, Vol. 79, pp. 353-359, 1999
(8) “Skeletal Muscle Buffering Capacity and Endurance Performance after High-Intensity Training by Well-Trained Cyclists, European Journal of Applied Physiology, Vol. 75, pp. 7-13, 1997

To learn about Owen's running camp in Malibu, California this summer, please visit www.RRNews.com, scroll to the bottom of the page, and click on the running-camp "splash."

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