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Effect of FIO2 on Physiological Responses and Cycling Performance at Moderate Altitude


Medicine & Science in Sports & Exercise: July 2003 - Volume 35 - Issue 7 - pp 1153-1159
BASIC SCIENCES: Original Investigations

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., Vol. 35, No. 7, pp. 1153–1159, 2003.

Purpose: To evaluate physiological responses and exercise performance during a “live high–train low via supplemental oxygen” (LH + TLO2) interval workout in trained endurance athletes.

Methods: Subjects (N = 19) were trained male cyclists who were permanent residents of moderate altitude (1800–1900 m). Testing was conducted at 1860 m (PB 610–612 Torr, PIO2 ∼128 Torr). Subjects completed three randomized, single-blind trials in which they performed a standardized interval workout while inspiring a medical-grade gas with FIO2 0.21 (PIO2 ∼128 Torr), FIO2 0.26 (PIO2 ∼159 Torr), and FIO2 0.60 (PIO2 ∼366 Torr). The standardized interval workout consisted of 6 × 100 kJ performed on a dynamically calibrated cycle ergometer at a self-selected workload and pedaling cadence with a work:recovery ratio of 1:1.5.

Results: Compared with the control trial (21% O2), average total time (min:s) for the 100-kJ work interval was 5% and 8% (P < 0.05) faster in the 26% O2 and 60% O2 trials, respectively. Consistent with the improvements in total time were increments in power output (W) equivalent to 5% (26% O2 trial) and 9% (60% O2 trial; P < 0.05). Whole-body V̇O2 (L·min−1) was higher by 7% and 14% (P < 0.05) in the 26% O2 and 60% O2 trials, respectively, and was highly correlated to the improvement in power output (r = 0.85, P < 0.05). Arterial oxyhemoglobin saturation (SpO2) was significantly higher by 5% (26% O2) and 8% (60% O2) in the supplemental oxygen trials.

Conclusion: We concluded that a typical LH + TLO2 training session results in significant increases in arterial oxyhemoglobin saturation, V̇O2 and average power output contributing to a significant improvement in exercise performance.

Live high–train low (LHTL) altitude training is used by contemporary elite athletes from several endurance sports in preparation for sea-level competition. Athletes who use LHTL live and/or sleep at moderate altitude (2000–2700 m), while simultaneously training at low elevation (≤1200 m). It has been demonstrated that living at 2400 m for 4 wk brought about significant increases in red blood cell mass and hemoglobin concentration in well-trained (11) and elite distance runners (26). Simultaneous training at a lower elevation (1200 m) allowed these athletes to achieve running velocities similar to their sea-level running velocities, purportedly inducing beneficial peripheral and neuromuscular adaptations. When the runners returned to sea level, significant improvements in V̇O2max and endurance performance (3000-m and 5000-m runs) were demonstrated, effects that were attributed to the hematological and neuromuscular adaptations that resulted from 4 wk of LHTL altitude training (11,26).

A number of different training strategies can be used in conjunction with LHTL altitude training (28). Athletes can live high in a natural, hypobaric hypoxic environment and train at a lower elevation that is in reasonable proximity (11,26). Alternately, athletes can sleep high in a simulated, normobaric hypoxic environment, (e.g., nitrogen-diluted apartment, hypoxic tent) and train low in a natural, normobaric normoxic environment (1,5,18,25). Another scenario allows athletes to live high in a natural, hypobaric hypoxic environment and train low in a simulated normoxic environment using supplemental oxygen (LH + TLO2) (3,15).

Several investigations conducted at sea level have documented the beneficial effects of acute utilization of supplemental oxygen (FIO2 ∼0.30–0.62) on physiological responses and exercise performance during continuous and intermittent exercise in well-trained (21) and elite rowers (16), endurance athletes (20,23,24), and track sprinters (17). The beneficial effects of acute hyperoxia (FIO2 ∼0.30–0.70) on submaximal and maximal exercise at sea level have been associated with a reduced rate of lactate accumulation in skeletal muscle and blood (6,7), maintenance of cerebral oxygenation (16), attenuated arterial oxyhemoglobin desaturation (20), maintenance of resting levels of ATP, ADP, and total NADH (12), and enhanced peak power output (9).

Currently there is a paucity of data regarding the acute effects of supplemental oxygen utilization during exercise at altitude. To our knowledge, only two previous studies have examined the use of hyperoxia by trained endurance athletes during exercise at altitude (3,15). Given that both of those investigations were long-term training studies, the results were primarily reflective of chronic adaptations as opposed to acute physiological responses. Accordingly, the purpose of this investigation was to evaluate the acute effects of supplemental oxygen (FIO2 0.26 and 0.60) on physiological responses and exercise performance during a high-intensity interval workout in trained endurance athletes residing permanently at altitude (1800–1900 m). In terms of practical application, this study gave us the opportunity to objectively evaluate the acute effects of LH + TLO2, which has the advantage of allowing athletes to live in a natural, hypobaric hypoxic environment and effectively “train low” with minimal travel and inconvenience. We hypothesized that the use of supplemental oxygen would allow endurance athletes to train at increased power output during high-intensity workouts at altitude via enhanced arterial oxyhemoglobin saturation and oxygen consumption, thereby supporting LH + TLO2 as a viable altitude training strategy.

1Athlete Performance Laboratory, United States Olympic Committee, Colorado Springs, CO;

2Department of Exercise Science, Health Promotion and Recreation, Colorado State University–Pueblo, Pueblo, CO; and

3Sport Science Department, USA Cycling, Colorado Springs, CO

Address for correspondence: Randall L. Wilber, Ph.D., Athlete Performance Laboratory, Sport Science Division, United States Olympic Committee, One Olympic Plaza, Colorado Springs, CO, 80909; E-mail:

Submitted for publication December 2002.

Accepted for publication February 2003.

©2003The American College of Sports Medicine