Abstract

Two experiments were performed to study the cardiac output (Q) vs. hemoglobin concentration (Hb) relationship during submaximum exercise. The first experiment examined the relationship between submaximum exercise Q and Hb in 28 females. A correlation of r = -O.83 was observed between Q and Hb during exercise at 88 W. By removing the influence of stroke volume (SV) from Q, the relationship between Q and Hb is compromised (r = -O.29, 88 W and r = -O.33, 118 W). The second experiment compared the VO2 max and submaximum exercise (118 W) Q responses in six males before and after blood donation. Experimentally reducing Hb 18.6 caused a 6.2 decrease in VO2 max. Additionally, submaximum exercise Q increased 12 6 days following hemodilution. The Q remained elevated 11 days (10 higher) and 16 days (9 higher) post-blood donation and progressively returned to pre-donation levels by 21 days postwithdrawal. The higher Qs during submaximum exercise were ascribed primarily to an 8 higher SV in comparison to pre-donation levels. Furthermore, it is suggested that the stimulus for the SV-induced Q vs. Hb association is relatedto maintaining maximal myocardial efficiency. Verf.-Referat