Impact of Erythropoietin on Hematological Adaptations and Physical Performance

Healthy physically active individuals will be recruited to participate in this longitudinal trial. After baseline assessments of body composition, resting metabolic rate (RMR), VO2peak and exercise familiarization; volunteers will complete physical performance and substrate oxidation testing. Physical performance will be assessed using time trial. Substrate oxidation will be assessed by volunteers performing 90-min of steady-state load carriage (30% body mass) exercise on a treadmill at 55 ± 5% of their VO2peak. 6-6-\[2H2\] glucose will be used as a tracer to assess glucose turnover. Indirect calorimetry will be used to determine carbohydrate and fat oxidation. Muscle biopsies will be performed to measure muscle glycogen, enzyme activity, and molecular markers of substrate metabolism before, immediately after, and 3-hrs post exercise. Multiple blood samples will be collected on substrate oxidation protocol days. To minimize carry over effects of muscle biopsies on subsequent exercise performance, volunteers will not exercise for 3 days. During the first two days of this period, volunteers will undergo carbon monoxide (CO) rebreathing to measure Hgb mass and blood volume. Volunteers will then receive EPO injections 3 times a week for 4 weeks. During the injection period all volunteers will have safety blood draws to assess Hct once a week. Volunteers will also complete a physical performance test once a week to determine time course change in performance with EPO compared to baseline. Exercise training will be controlled during the injection phase, consisting of a combination of endurance- and resistance-type exercise. During the final week of the injection phase body composition, resting metabolic rate (RMR) and VO2peak will be reassessed. At the end of the 4-week injection phase volunteers will complete a final physical performance test and substrate oxidation protocol, followed by two CO rebreathing tests on subsequent days. All food and beverages (except water) will be provided to volunteers beginning at the pre injection physical performance and substrate oxidation through the duration of the study. All data collection will occur at USARIEM.