PERFORMANCE CHANGES AT ALTITUDE ARE NOT ACCOUNTED FOR BY ALTERED HEMOGLOBIN MASS OR OTHER HEMODYNAMICS
Nelson, J. L., Doan, B. K., Ryan, B., Byrnes, W. C., & Brothers, M. D. (2009). Relationship between total hemoglobin mass and aerobic performance of sea level residents exposed to 2210m. ACSM 56th Annual Meeting, Seattle, Washington. Presentation number 2362.
"It is reported that up to 70% of aerobic performance is related to the O2 carrying capacity as measured by total hemoglobin mass (THM). However, the relationship between THM and performance among sea level (SL) subjects following acute and chronic residence at moderate altitude (MA) has not been examined."
This study examined the relationship between total hemoglobin mass and 1.5 mile run time acutely and after 6 and 10 weeks of chronic moderate altitude exposure among sea level and moderate altitude Ss at the U.S. Air Force Academy. It was hypothesized that a significant correlation would exist between total hemoglobin mass and 1.5 mile run time acutely, that former sea level Ss would display a significant increase in total hemoglobin mass and improved run time chronically, and these changes would correlate significantly. Male and female freshman Ss (55 from sea level and 11 already adapted to moderate altitude) completed a 1.5 mile run one day after in-processing at the U.S. Air Force Academy (2,210 m) as part of a standard fitness test. Total hemoglobin mass was measured within 72 hours of arrival utilizing the optimized CO re-breathing protocol. The 1.5 mile run and total hemoglobin mass assessments were repeated following 6 and 10 weeks of chronic residence at the U.S. Air Force Academy.
Acutely, all hematological variables examined correlated significantly with aerobic performance among sea level Ss, with total hemoglobin mass predicting 49% of the observed variability. After 6 and 10 weeks at moderate altitude, sea level cadets displayed a 5% and 8.5% gain in total hemoglobin mass, and 12.7% and 15.8% improvement in 1.5 mile run time, respectively, and all hematological variables again correlated significantly. However, the change in these blood values vs. the altered run time among sea level Ss after ~6 weeks resulted in non-significant correlations, and only the altered total hemoglobin mass and altered erythrocyte volume correlated significantly after ~10 weeks. No significant correlations occurred among moderate altitude controls.
Implication. Strong correlations existed between blood values and run time but they explained less than half of the variability with sea level adaptation. Significant improvements in performance were seen with living at altitude but blood adaptations accounted for only 16% of the variability involved in the alteration. Other adaptations besides total hemoglobin mass may be needed for improved aerobic performance and moderate altitude acclimatization. Performance improvements after moderate altitude adaptation cannot be explained adequately as the result of altered hemoglobin mass or other hemodynamic variables.
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