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12 jun 2012

Use of supplemental oxygen in living high + training low.

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Altitude training has been used by endurance athletes for many years based on the belief that it serves to enhance sea level performance.
Autor(es): Randall L. Wilber
Entidades(es): Université Paris 13
Congreso: International symposium of altitude training
Granada 2008
ISBN:9788461235193
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Use of supplemental oxygen in living high + training low.

Altitude training has been used by endurance athletes for many years based on the belief that it serves to enhance sea level performance. The original model of altitude training was one in which athletes lived and trained in a natural/terrestrial hypobaric hypoxic environment at moderate altitude (1500-3000 m). This method of altitude training came to be known as “live high-train high” (LH + TH) and is still used today by many athletes. Although LH + TH altitude training has been studied extensively over several decades, it remains unclear whether it has an enhancing effect on sea level performance. Whereas some investigations have demonstrated significant improvements in erythrocyte parameters, maximal oxygen uptake (VO2max) and/or sea level endurance performance following LH + TH altitude training, others have failed to do so. One of the potential limitations of LH + TH altitude training is that many athletes are unable to produce the level of training “intensity” (e.g., running velocity) and oxygen flux necessary to bring about or preserve the physiological changes that have a positive impact on performance. It is not uncommon to hear athletes remark that they seem to lose “speed” or “turnover” as a result of LH + TH altitude training, which ultimately has a negative impact on their sea level performance. In response to this potential limitation of LH + TH altitude training, the “live high-train low” (LH + TL) altitude training model was developed in the early 1990s by Drs.

Benjamin Levine and James Stray-Gundersen of the United States. The essence of LH + TL is that it allows athletes to “live high” for the purpose of facilitating altitude acclimatization (e.g., an increase in endogenous erythropoietin [EPO] and resultant increase in erythrocyte volume, and other non-erythropoietic adaptations), while simultaneously allowing athletes to “train low” to induce beneficial metabolic and neuromuscular adaptations. Based on the promising findings of the initial investigations of natural/terrestrial LH + TL, several modifications of LH + TL were developed in the 1990s. Among these modifications is one in which athletes live in a natural, hypobaric hypoxic environment but train at simulated “sea level” with the aid of supplemental oxygen (LH + TLO2). LH + TLO2 is used effectively at the U.S. Olympic Training Center in Colorado Springs, Colorado, USA, where U.S. national team athletes live at approximately 2000 m to 3000 m in the foothills of the Rocky Mountain range. The average barometric pressure (PB) in Colorado Springs is approximately 610 Torr, which yields a partial pressure of inspired oxygen (PIO2) of approximately 128 Torr. By inspiring a certified medical grade gas with a fraction of inspired oxygen (FIO2) approximately 0.26, athletes can complete high-intensity training sessions in a simulated “sea level” environment at a PIO2 equivalent to approximately 150 Torr. In addition to U.S. national team athletes at the U.S.

Olympic Training Center in Colorado Springs, the highly-successful U.S. long track speedskating team has utilized LH + TLO2 in conjunction with high-intensity training sessions done at the Utah Olympic Oval (1425 m) in Salt Lake City. Only a few studies have evaluated the efficacy of LH + TLO2 on athletic performance (1-5). Wilber et al. (3) evaluated the acute effects of supplemental oxygen on physiological responses and exercise performance during a high-intensity cycling interval workout (6 x 100 kilojoules [kJ]; work:recovery ratio = 1:1.5) in trained endurance athletes who were altitude residents (1800-1900 m). Compared with a control trial (FIO2 0.21), average total time for the 100-kJ work interval was 5% and 8% (P < 0.05) faster in the FIO2 0.26 and FIO2 0.60 trials, respectively (Figure 1A). Consistent with improvements in total time were increments in power output equivalent to 5% in the FIO2 0.26 trial and 9% in the FIO2 0.60 trial (P < 0.05) (Figure 1B). Whole-body VO2 (L . min-1) was higher by 7% and 14% (P < 0.05) in the FIO2 0.26 and FIO2 0.60 trials, respectively, and was highly correlated with the improvement in power output (r = 0.85; P < 0.05). Arterial oxyhemoglobin saturation (SpO2) was significantly higher by 5% (FIO2 0.26) and 8% (FIO2 0.60) in the supplemental oxygen trials.

Gráficos 1 y 2. Use of supplemental oxygen in living high + training low.

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In a subsequent study, Wilber et al. (5) utilized near-infrared spectroscopy (NIRS) and reported that hemoglobin/myoglobin (Hb/Mb)-deoxygenation of m. vastus lateralis was 8% and 12% less at blood lactate threshold and VO2max, respectively, during an FIO2 0.60 trial versus a control trial (FIO2 0.21) (Figure 2), suggesting that supplemental oxygen enhances the availability of oxygen at the level of the capillary bed of the working skeletal muscle. Finally, Wilber et al. (4) reported that there was no significant difference in cellular oxidative stress during exercise when comparing supplemental oxygen trials (FIO2 0.26, FIO2 0.60) with a control trial (FIO2 0.21), as determined by serum measurements of lipid hydroperoxides (LOOH) and reduced glutathione (GSH), as well as urinary measurements of malondialdehyde (MDA) and 8-hydroxy-deoxygenase (9-OHdG). Based on these results (3-5), it was concluded that LH + TLO2 results in significant increases in arterial oxyhemoglobin saturation and greater unloading of oxygen at the level of the capillary bed of the working muscle, contributing to significant increases in power output and exercise performance, without inducing additional cellular oxidative stress. The long-term training effects of LH + TLO2 were evaluated by Morris et al. (2). U.S. national team junior cyclists completed a 21-day training period during which they lived and performed their moderate-intensity workouts at 1860 m (Colorado Springs), and performed their high-intensity interval training at simulated sea level using supplemental oxygen (FIO2 0.26; PIO2 150 Torr).

Interval workouts were done 3 days per week, and each interval workout required the athletes to complete 5 x 5-minute cycling efforts at 105% to 110% of maximal steady-state heart rate. A control group of fitness-matched teammates completed the same training program at 1860 m using normoxic gas (FIO2 0.21; PIO2 128 Torr). Athletes using supplemental oxygen were able to train at a significantly higher percentage of their altitude-determined lactate threshold (126%) versus their counterparts who trained in normoxic conditions (109%). Following the 21-day training period, the athletes performed a 120-kJ cycling performance time trial in simulated sea level conditions (FIO2 0.26; PIO2 150 Torr). Results of the cycling performance test showed improvements of 2 seconds (P > 0.05 vs. pre-training) and 15 seconds (P < 0.05 vs. pre-training) for the normoxic-trained and LH + TLO2-trained cyclists, respectively (2). In agreement with Wilber et al. (3), the results of Morris et al. (2) demonstrated that high-intensity workouts at moderate altitude (1860 m) are enhanced through the use of supplemental oxygen. Further, Morris et al. (2) was the first to show that sea level endurance performance in elite athletes can be improved as a result of LH + TLO2. In summary, these empirical results, along with anecdotal evidence, provide support for the practical application of LH + TLO2 as an altitude training strategy. LH + TLO2 allows athletes to effectively live/sleep high and train low with minimal travel or inconvenience, thereby enhancing the overall training regimen.

References

1. Chick, T.W., D.M. Stark, and G.H. Murata. Hyperoxic training increases work capacity after maximal training at moderate altitude. Chest 104:1759-1762, 1993.

2. Morris, D.M., J.T. Kearney, and E.R. Burke. The effects of breathing supplemental oxygen during altitude training on cycling performance. J. Sci. Med. Sport. 3:165-175, 2000.

3. Wilber, R.L., P.L. Holm, D.M. Morris, G.M. Dallam, and S.D. Callan. Effect of FIO2 on physiological responses and cycling performance at moderate altitude. Med. Sci. Sports Exerc. 35:1153-1159, 2003.

4. Wilber, R.L., P.L. Holm, D.M. Morris, G.M. Dallam, A.W. Subudhi, D.M. Murray, and S.D. Callan. Effect of FIO2 on oxidative stress during interval training at moderate altitude. Med. Sci. Sports Exerc. 36:1888-1894, 2004.

5. Wilber, R.L., J. Im, P.L. Holm, C.D. Toms, D.M. Morris, G.M. Dallam, J.R. Trombold, and B. Chance. Effect of FIO2 on hemoglobin/myoglobin-deoxygenation during highintensity exercise at moderate altitude. Med. Sci. Sports Exerc. 37 (Suppl. 5):S297, 2005.

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