Effects of exercise mode on hematologic adaptations to endurance training in adult females

The subjects were 26 healthy, sedentary adult females with the following characteristics: maximal oxygen consumption (VO2max) = 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 ergometer training (CY; N = 10) to test the hypothesis that hematologic adaptations to endurance exercise training are specific to mode of exercise.

Training, conducted 3-5 (3.4 +/- 0.06) d.week-1 at 80% of mode specific VO2max for 12 weeks, was supervised and progressive, with estimated exercise energy expenditure equated across training groups. Plasma volume (PV, T-1824 dilution); calculated total blood (THb) and red cell volumes (RCV); calculated total hemoglobin (THb) and other hematologic variables were measured at baseline and weeks 2, 4, 8 and 12 of training.

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. Hemodilution was observed in both training groups, reflected by decreases (p < 0.05) in hematocrit (Hct), hemoglobin (Hb) and RC count. Mean corpuscular Hb (MCH) and Hb content (MCHC) increased (p < 0.05) with training. These changes, as well as trend toward increased (p = 0.08) mean corpuscular volume (MCV), suggested the probable presence of a RC population with a lower mean age and decreased oxyhemoglobin affinity. The possibility of Type II error cannot be discounted in these trends, which suggest that PV, TBV and RCV may be affected by mode of endurance exercise in females.