EFFECTS OF EXERCISE MODE ON HEMATOLOGIC ADAPTATIONS TO ENDURANCE TRAINING IN ADULT FEMALES

Background: The subjects were 26 healthy, sedentary adult females with the following characteristics: maximal oxygen consumption ((V) over d ot o(2)max) = 32.0 +/- 7.2 ml.kg(-1).min(-1); age = 32 +/- 5 yr; body mass index (BMI) = 23.2 +/- 3.4 kg.m(-2) who were randomly assigned to control (CON; N = 8); treadmill training (TM; N = 8); or cycle ergome ter training (CY; N = 10) to test the hypothesis that hematologic adap tations to endurance exercise training are specific to mode of exercis e. Methods: Training, conducted 3-5 (3.4 +/- 0.06) d.week(-1) at 80% o f mode specific (V) over dot o(2)max for 12 weeks, was supervised and progressive, with estimated exercise energy expenditure equated across training groups. Plasma volume (PV, T-1824 dilution); calculated tota l blood (THb) and red cell volumes (RCV); calculated total hemoglobin (THb) and other hematologic variables were measured at baseline and we eks 2, 4, 8 and 12 of training. Results: Across 12 weeks of training, PV was decreased (95% of baseline) in the TM group but increased (106% of baseline) in the CY group (p = 0.06). Similar trends were observed for RCV (p = 0.15) and TBV (p = 0.08). These results are in contrast to reported changes in PV, TBV and RCV in males following training. He modilution was observed in both training groups, reflected by decrease s (p < 0.05) in hematocrit (Hct), hemoglobin (Hb) and RC count. Mean c orpuscular Hb (MCH) and Hb content (MCHC) increased (p < 0.05) with tr aining. These changes, as well a trend toward increased (p = 0.08) mea n corpuscular volume (MCV), suggested the probable presence of a RC po pulation with a lower mean age and decreased oxyhemoglobin affinity. T he possibility of type II error cannot be discounted in these trends, which suggest that PV, TBV and RCV may be affected by mode of enduranc e exercise in females.