Effect of FIO2 on oxidative stress during interval training at moderate altitude.
OBJECTIVE
To evaluate the effect of different fractions of inspired oxygen (FIO2) on oxidative stress during a high-intensity interval workout in trained endurance athletes residing at altitude.


METHODS
Subjects (N = 19) were trained male cyclists who were residents of moderate altitude (1800-1900 m). Testing was conducted at 1860 m (PB 610-612 torr, PIO2 approximately 128 torr). Subjects performed three randomized, single-blind trials consisting of a standardized interval workout (6 x 100 kJ) while inspiring a medical-grade gas with FIO2 0.21 (PIO2 approximately 128 torr), FIO2 0.26 (PIO2 approximately 159 torr), and FIO2 0.60 (PIO2 approximately 366 torr). Serum lipid hydroperoxides (LOOH) and whole-blood reduced glutathione (GSH) were measured 60 min preexercise and immediately postexercise, and analyzed using standard colorimetric assays. Urinary malondialdehyde (MDA) and 8-hydroxydeoxyguanosine (8-OHdG) were measured 24 h preexercise and 24 h postexercise, and analyzed via HPLC and ELISA, respectively.


RESULTS
Compared with the control trial (FIO2 0.21), total time (min:s) for the 100-kJ work interval was faster (5% in FIO2 0.26; 8% in FIO2 0.60 (P < 0.05)) and power output (W) was higher (5% in FIO2 0.26, 8% in FIO2 0.60 (P < 0.05)) in the supplemental oxygen trials. There was a significant pre- versus postexercise main effect (P < 0.05) for LOOH and GSH; however, there were no significant differences in LOOH or GSH between the FIO2 trials. MDA and 8-OHdG were unaffected by either the interval training session or FIO2.


CONCLUSIONS
Supplemental oxygen used in conjunction with high-intensity interval training at altitude ("live high + train low via supplemental O2" (LH + TLO2)) results in a significant improvement in exercise performance without inducing additional free radical oxidative stress as reflected in hematological and urinary biomarkers.
Wilber
Randall L
RL
Athlete Performance Laboratory, United States Olympic Committee, Colorado Springs, CO 80909, USA. randy.wilber@usoc.org
Holm
Paige L
PL
Morris
David M
DM
Dallam
George M
GM
Subudhi
Andrew W
AW
Murray
Dennis M
DM
Callan
Samuel D
SD
D000328:Adult; D000531:Altitude; D001642:Bicycling / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005978:Glutathione / Q000097:blood; D006801:Humans; D001239:Inhalation / Q000502:physiology*; D008054:Lipid Peroxides / Q000097:blood; D008297:Male; D008315:Malondialdehyde / Q000652:urine; D018384:Oxidative Stress / Q000502:physiology*; D010100:Oxygen / Q000378:metabolism*; D010806:Physical Education and Training / Q000379:methods*; D010807:Physical Endurance / Q000502:physiology; D016037:Single-Blind Method; D013647:Task Performance and Analysis
D008054:Lipid Peroxides; D008315:Malondialdehyde; D005978:Glutathione; D010100:Oxygen