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The Effects of Nightly Normobaric Hypoxia on Running Economy and Hemoglobin Mass: 2728Board #2 9:AM – 10:AM

Neya, Mitsuo; Maegawa, Taketeru; Kumai, Yasuko; Enoki, Taisuke; Kawahara, Takashi; Gore, Christopher J. FACSM

Medicine & Science in Sports & Exercise: May 2006 - Volume 38 - Issue 5 - p S524
Saturday Morning Poster Presentations: Posters displayed from 7:30–11:00 a.m.: One-hour author presentation times are staggered from 8:00–9:00 a.m., 9:00–10:00 a.m., and 10:00–11:00 a.m.: G-10 Free Communication/Poster – Altitude and Hypoxia: SATURDAY, JUNE 3, 2006 8:00 AM – 11:00 AM ROOM: Hall B

1Dept. of Arts and Sciences, The University of Tokyo, Tokyo, Japan.

2Japan Institute of Sports Sciences, Tokyo, Japan.

PURPOSE: To investigate the effects of nightly intermittent hypoxia on the total hemoglobin mass (THb) maximum oxygen consumption (VO2max) and running economy.

METHODS: Sixteen college-level long- and middle-distance runners (mean ± SD age, height, mass, VO2max = 22±2 yr, 169±5 cm,58.4±6.0 kg, 60.1±7.5 ml/kg/min) were assigned to a hypoxic group (HYP, n=10) who rested and slept in hypoxic accommodation (O2 concentration =14.5%; = 3000m) ∼10–12 h/night and trained at sea level, or to a control group (CON, n=6) who slept and trained at sea level. The hypoxic period was 29 nights and VO and THb were measured before and 5–7 days after.

THb was measured using the carbon monoxide method twice during the 10 days before the intervention and our typical error was 2.4%. Submaximal running economy (RE) was measured on a motorized treadmill at 12, 14, 16 and 18 km/h with 4 min at each speed. The classic Douglas bag method was used to measure VO

RESULTS: Twenty-nine consecutive-nights of “live simulated high, train sea level” did not increase THb (HYP-pre 807±64 vs post 798±73 g; CON-pre 872±34 vs post 877±24 g) nor was there a corresponding change in VO2max (HYP-pre 61.7±3.2 vs post 59.1±4.6 ml/kg/min; CON-pre 59.8±7.1 vs post 56.8±4.5 ml/kg/min). These results indicate that this duration of intermittent exposure to hypoxia was insufficient stimulate increased red blood cell production. Only the HYP group had a 5.0% improved RE at 18 km/h (P < 0.01). There were no significant changes in submaximal blood lactate concentration (BLa) and ventilation (VE). For instance at 18 km/h BLa was pre (HYP 6.2±3.2; CON 6.0±2.6 mmol/L) and post (HYP 6.1±2.4; CON 4.9±1.7 mmol/L), and VE was pre (HYP 89.3±13.2; CON 81.0±8.2L/min) and post (HYP85.1±10.3; CON 80.5±16.7 L/min). These two results exclude the possibility that greater carbohydrate utilization or reduced energy requirement of respiratory muscle were induced by the exposure to hypoxia.

CONCLUSIONS: Although this hypoxic protocol did not cause changes in THb and VO, the improved economy at submaximal running speed implies that sleeping in hypoxia for 29 nights can enhance athletic performance.

© 2006 American College of Sports Medicine