The mean red cell volume in long distance runners

Area of Science:

• Exercise Physiology
• Hematology
• Sports Medicine

Background:

• Red blood cell (RBC) indices are crucial for oxygen transport and blood viscosity.
• Endurance running, particularly ultra-marathons, can induce significant physiological stress.
• Understanding RBC volume regulation during and after prolonged exercise is important for athlete health and performance.

Purpose of the Study:

• To investigate changes in red cell indices in trained runners after a 100 km race.
• To compare Coulter Counter (CC) derived indices with calculated values from centrifuged hematocrit (ctrf).
• To explore the role of plasma osmolality in regulating red cell volume post-exercise.

Main Methods:

• Determination of red cell indices in 6 trained runners before and after a 100 km race.
• Comparison of Coulter Counter (CC) measurements with calculated values from centrifuged hematocrit (ctrf), RBC count, and hemoglobin.
• Analysis of changes in mean corpuscular volume (MCV) and mean corpuscular hemoglobin concentration (MCHC).

Main Results:

• Mean corpuscular volume (MCV) determined by centrifugation (MCV(ctrf)) decreased by 4.9% (p<0.001).
• Mean corpuscular volume (MCV) determined by Coulter Counter (MCV(CC)) increased by 1.9% (p<0.05).
• Mean corpuscular hemoglobin concentration (MCHC) showed opposing trends: MCHC(ctrf) increased by 4%, while MCHC(CC) decreased by 3%.

Conclusions:

• The increase in MCV(CC) suggests increased intraerythrocyte osmolality and cell swelling due to water shift into RBCs.
• The decrease in MCV(ctrf) was not directly correlated with plasma osmolality, indicating other regulatory factors.
• RBC volume changes post-race may be a physiological mechanism to maintain favorable blood viscosity and hematocrit.