Hi folks. I was going through some of university work from my undergrad and came across a paper I had written about training at elevation. I thought I would share it with you. Feel free to be as critical as you want about it, I was in my third year of the degree at the time and I will not take offense if you think this is a pile of garbage.
Altitude training, or in a more general sense hypoxia, has been used as a means of improving an athlete's performance in endurance sports. Three methods of inducing hypoxia via altitude training exist; Live High-Train High, Live High-Train Low, Live Low-Train High. For simplicity this paper will not separate these modalities, but will look at the general effects of hypoxia on an athlete's performance. Many reasons have been suggested as to why hypoxia can improve performance. Two of the more controversial reasons are the change in red blood cell volume (RBCV) and haemoglobin mass which results better oxygen transport, and changes at the muscle site which result in better oxygen diffusion/uptake. This paper will discuss how the altitude training affects RBCV and haemoglobin with regards to oxygen carrying capacity versus changes at the muscle site.
"For more than 40 years, the effects of classical altitude training on sea-level performance have been the subject of many scientific investigations in individual endurance sports" (Friedmann-Bette, 2008). Bartsch & Saltin (2008) suggest that the aim of altitude training is "securing the oxygen supply to tissues and organs of the body with an optimal oxygen tension of the arterial blood." Many mechanisms have been suggested as the limiting factor for improved performance. Researchers such as Levine & Stray-Gunderson are firm believers that that change in RBCV as well has haemoglobin account for a better oxygen carry capacity and thus improved VO2max. Still others, such as Michael J. Ashenden á Christopher J. Gore Geoffrey P. Dobson á Allan G. Hahn (1999) have found that RBCV does not change when living at a high altitude. Finally, Researcher Hans Hoppeler been involved in numerous studies that point to changes in the skeletal muscle as being a significant factor.
Changes in Blood Characteristics
Those who advocate that changes in blood characteristics more greatly influence an athlete's performance than any other factor will point to the apparent increase in RBCV and haemoglobin mass. "One of the most documented physiological adaptations to [hypoxia], is the increased release of erythropoietin, which causes a transient increase in red blood cell mass" (Bailey & Davies, 1997). Coupled with the fact that an increase in red blood cell mass has been shown to elicit an increase in VO2max, it is not difficult to see why many researches advocate changes in blood characteristics as the main reason for improved performance.
Halle, Marti, Wehrlin, and Zuest (2006) completed a 24 day Live High-Train Low study involving ten elite Swiss athletes who lived at an altitude of 2500m above sea level compare to seven Swiss national team skiers who served as a control. In their study they found that the athletes who lived at altitude had an increase in RBCV of 5% from pre-test to post-test as well as an increase in haemoglobin of 5.3%. It was also observed that the Live High-Train Low athletes exhibited a 4.3% increase in VO2max. Levine & Stray Gunderson (1997) report similar findings. They found that athlete's living at moderate altitude (2500m) and training at sea-level observed a 9% increase in RBCV as well as a 5% increase in VO2max.
As can be seen from the above examples there seems to be clear correlation between increased RBCV and haemoglobin mass on VO2max. It can also be easily observed that persons living and training at sea-level do not elicit the same benefits as their altitude trained counterparts.
Changes at the Muscle Site
Those who are not supporters of an increase in RBCV and haemoglobin mass as the factor will point to numerous studies that do not show any increase in haemoglobin as a result of altitude training. Billat et al. (2006) found that haemoglobin and hematocrit counts for athletes were similar before and after altitude exposure. Similarly, Ashenden, Dobson, Gore, and Hahn found that total haemoglobin mass did not change in male endurance athletes after exposure to simulated 3000m altitude for 23 nights.
Researchers suggest that changes at the muscle site, not changes in blood characteristics, account for improved performance in endurance athletes. Hoppeler, Klossner, & Vogt (2008) state that "it is well established that local muscle tissue hypoxia is an important consequence and possibly a relevant adaptive signal of endurance training in humans."
Billat et al. found in a study involving 18 athletes (with nine training under normal conditions and nine training under hypoxic conditions) that only the hypoxic group realized an a significant change in VO2max (~5%) and these changes were not due to blood oxygen-carrying capacity.
Dufour et al.(2006) found that hypoxia induced modulations in mitochondrial function including decreased sensitivity of mitochondrial respiration to cytostolic ADP and increased coupling to phospho-transfer kinases, which contributes to a better integration between ATP demand and supply. Fluck, Hoppeler, Vogt , & Weibel (2003) found that there is actually a decrease in mitochondrial content in the muscle. However, they did find that better coupling between ATP demand and supply pathways as well as better metabolite homeostasis account for improve performance.
According to Freidmann-Bette, Mizuno et al. (1990) and Saltin et al. (1995) report that muscle biopsies taken from the gastrocnemius or triceps brachii of elite cross-country skiers after two weeks of living at altitude and biopsies from the vastus lateralis and grastrocnemius of elite runners living and training at a similar altitude, showed significantly increased muscle buffering capacity. An increased muscle buffering capacity will increase time to fatigue and thus improved performance.
Mazzeo (2008) states that while RBCV increases with altitude training, the net oxygen delivery to exercising muscle does not increase accordingly. He continues to say that "this is the result of an actual decrease in muscle blood flow during exercise, thereby offsetting the improvements in oxygen content. He suggests that the reason VO2max can increase as a result of hypoxia is that the muscles ability to extract oxygen because of the increased (a-v)O2 due to the difference in pressure from sea-level to altitude.
In reviewing the available literature pertaining to the differing opinions of why altitude training can improve performance I am inclined to believe that changes in blood characteristics may play a greater role than changes at the muscle site. One of the main reasons I support blood characteristics as the most convincing argument is the lack of definitive research and support of the changes at the muscle site. In fact, studies, such as those done Green et al., 1989; Hoppeler et al., 1990; MacDougall et al., 1991 as sited in Hoppeler, Klossner, & Vogt found that permanent exposure to severe hypoxia (~5000m) leads to a appreciable deterioration of skeletal muscle.
While Mizuno et al. found that muscle biopsies showed significantly increased muscle buffer capacity in elite cross-country skiers (Freidmann-Bette), a more recent study by Levine and Stray-Gunderson found that muscle biopsies taken from runners did not yield an increase in the buffering capacity of muscle or oxidative enzymes.
Also, increased RBCV and haemoglobin mass is very well documented in studies byLevine & Stray-Gunderson; Prommer & Schmidt (2008); Convertino; Chapman, Levine & Stray-Gunderson (2001), and many other studies.
In looking at the effects of hypoxia on an athlete's performance one must not only look at oxygen carry capacity and the ability of the muscles to to use that oxygen. There are a number of other factors that can come into play such as iron deficiency due to increased haemoglobin (Bailey & Davies), an increased cardiac output and substrate utilization by the muscle (Mazzeo) as well as structural adaptations of the muscle ( Fluck, Hoppeler, Vogt , & Weibel). While I agree that the changes in blood characteristics play a greater role that the changes at the muscle site, I do not feel that lone benefit of hypoxia. Rather, I would suggest that a combination of factors are responsible for improve endurance performance. Mazzeo suggest numerous adaptations to hypoxia, and this presents a convincing argument that compounding factors lead to improved sea-level performance.
Further research is required in this field. I would suggest that should studies completed at a moderate to high altitude (>=2500m), for a duration of at least 16 hours a day for four weeks with the same type of athlete (i.e. endurance runner) and that these studies investigate all plausible adaptations to hypoxia to expand upon our current base of knowledge.
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Bailey, D. M., & Davies, B. (1997). Physiological implications of altitude training for endurance performance at sea level: A review. British Journal of Sports Medicine, 31(3), 183-190.
Bärtsch, P., & Saltin, B. (2008). General introduction to altitude adaptation and mountain sickness. Scandinavian Journal of Medicine & Science in Sports, 18, 1-10.
Chapman, R. F., Levine, B. D., & Stray-Gundersen, J. (2001). "Living high- training low" altitude training improves sea level performance in male and female elite runners. Journal of Applied Physiology, 91(3), 1113-1120.
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Dufour, S. P.,, Doutreleau, S., Geny, B., Lonsdorfer-Wolf, E., Ponsot, E., Zoll, J. et al. (2006). Exercise training in normobaric hypoxia in endurance runners. I. improvement in aerobic performance capacity. Journal of Applied Physiology, 100(4), 1238-1248.
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Hoppeler, H., Klossner, S., & Vogt, M. (2008). Training in hypoxia and its effects on skeletal muscle tissue. Scandinavian Journal of Medicine & Science in Sports, 18, 38-49.
Levine, B. D., & Stray-Gundersen, J. (1997). "Living high-training low": Effect of moderate-altitude acclimatization with low-altitude training on performance. Journal of Applied Physiology, 83(1), 102-112. Mazzeo, R. S. (2008). Physiological responses to exercise at altitude: An update. Sports Medicine, 38(1), 1-8.
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