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Normobaric intermittent hypoxic exposure improves time‐trial performance in hypoxia but not in normoxia
Author(s) -
Fulco Charles S,
Muza Stephen,
Beidleman Beth,
Jones Juli,
Lammi Eric,
Staab Janet,
Cymerman Allen
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.a822-c
Subject(s) - hypoxia (environmental) , medicine , cardiology , anesthesia , oxygen , chemistry , organic chemistry
Time‐trial performance is impaired during initial exposure to normobaric hypoxia. This study determined if repeated intermittent hypoxic exposures (IHE) could ameliorate the performance impairment in hypoxia without affecting performance in normoxia. For 3 hrs a day for 6 consecutive days, 6 men (mean±SD; 21±2 yr, 178±6 cm, 76±8 kg) resided in a room at sea level (760 mmHg) where the partial pressure of inspired oxygen (PIO 2 ) was reduced by nitrogen dilution. Daily IHE consisted of 2 hrs of rest at a PIO 2 of 90 mmHg (4500 m equivalent) followed 1 hr of cycle exercise at ~55% of peak O 2 uptake (VO 2peak ) at a PIO 2 of 110 mmHg (3000 m equivalent). Before and after the 6 IHE, steady‐state (SS) exercise was performed under conditions of normoxia (PIO 2 = 159 mmHg) and hypoxia (PIO 2 = 93 mmHg, 4300 m equivalent) for 20 min at 45% and then at 65% of VO 2peak , followed by a peak effort 720 kJ time trial. From before to after IHE, SS exercise VO 2 , arterial oxygen saturation, and perceived exertion were not changed in either normoxia or hypoxia whereas heart rate was similarly lower (P<0.05) in both ambient conditions. Time‐trial performance was improved after IHE in hypoxia (100±18 vs 89±15 min, P<0.01) but not in normoxia (71±10 vs 69±12 min, P>0.05). Because of the similarity of SS exercise responses in hypoxia and normoxia before and after IHE, the reason(s) for the time‐trial performance improvement in hypoxia but not normoxia remains elusive.