Brothers, M. D., Doan, B. K., Wile, A. L., Weinstein, J. L., Zupan, M. F., Wilber, R. L., & Byrnes, W. C. (2008). Chronic hematological and physiological adaptations following 48 weeks of moderate altitude residence. ACSM 55th Annual Meeting Indianapolis. Presentation number, 735.

This longitudinal study determined the magnitude and time course of adaptation of selected hematological and performance parameters following 46 weeks at a uniquely well-controlled moderate altitude setting (2,210 m). US Air Force Academy male cadets (N = 55) were divided into groups based upon prior residence at sea level or moderate altitude. Hematological and performance parameters were repeatedly assessed during the entire first year at moderate altitude. Hematological data consisted of a CBC with reticulocyte parameters, serum ferritin, erythropoietin, and soluble transferrin receptor analysis. Performance testing included aerobic (1.5 mile run) and anaerobic (push-ups, sit-ups, pull-ups, and standing long jump) field tests, maximal aerobic capacity, and running economy.

Significant hematological differences between seal level and moderate-altitude Ss were observed for up to 30 weeks. Moderate-altitude Ss initially had a significantly higher hemoglobin concentration (+2.5%), hematocrit (+1.0%), and serum ferritin (+59.0%), and significantly lower soluble transferrin receptor (-11.4%) values than their sea-level peers. Significant differences existed between altitude groups in performance parameters for the entire year, with sea-level Ss having a significantly lower VO2peak, slower 1.5 mile run time, poorer running economy, and lower anaerobic composite fitness test score compared to moderate-altitude Ss.

Hematological acclimatization to 2210 m by former sea-level residents requires 30+ weeks. Altitude-induced erythropoiesis among sea-level Ss failed to ameliorate physical performance differences between altitude conditions. Physiological adaptations and hematological adjustments which require more than 45 weeks may be needed for complete moderate altitude acclimatization.

Implication. Altitude adaptations are not satisfactorily achieved through short exposures to moderate altitudes. Although erythropoietin level increases as part of the adaptation process in original sea level persons, they are insufficient to produce performance changes to match the higher performance levels of already-adapted Ss. Physiological and hematological changes do not account for sufficient performance changes. After 46 weeks, sea level Ss are still adapting and performances will not improve to a level of pre-adapted individuals.

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