Endurance running trial in tropical environment: a blood rheological study.

Purpose: The aim of this study was to clarify whether exercising in a tropical climate induces blood rheology alterations despite ad libitum hydration.

Methods: Hematological, biochemical and hemorheological changes were investigated in young healthy adults (N = 9 men, 20.7 ± 0.8 yrs) after a 10-km race in hot and humid conditions. Subjects' maximal aerobic abilities were tested using a maximal ramp exercise. Blood was sampled at rest (TR), at the end of the race (TEx), and after 24 hours of recovery (T24). Ad libitum hydration was allowed during the race. Blood viscosity (ηb), red blood cell deformability (EI), aggregation (AI) and disaggregation shear rate (γ) were measured.

Results: Hematocrit, hemoglobin and plasma concentration of chlorine, sodium and potassium did not change in response to exercise. No functional consequence was observed on RBC deformability since EI remained unchanged. Percentages of echinocytes, schizocytes and stomatocytes remained in the subclinical range at all times. AI, γ and ηb did not present change.

Conclusion: Running exercise in tropical climate with ad libitum hydration does not alter the main rheological properties of blood.