Regulation of perfusive O2 transport during exercise in humans: effects of changes in haemoglobin concentration.

Abstract

SUMMARY1. Recently it was suggested that submaximal cardiac output (Q) could vary in response to changes in arterial 02 concentration (Ca,02) so that arterial 02 delivery QaIo2 = Q X Ca O2 in ml min-) is kept constant.2. This hypothesis was tested on eight healthy male subjects, at rest and during exercise (50, 100 and 150 W) in three conditions: normaemia (N), after 6 weeks of endurance training (T), and 2 days after subsequent autologous blood reinfusion (P). 6. In conclusion, the tested hypothesis was supported by the present results. The observed constancy of Qv 2 suggested that Qv 2 may play a key role in regulating the cardiovascular response to exercise.

Arterial O2 content and tension in regulation of cardiac output and leg blood flow during exercise in humans

“…The explanation for this discrepancy from the report of Ferretti et al (5) is likely that the slope of V O 2 ϫ Q TOT (Ca O 2 ) is Ͻ1, which violates a key assumption in their theoretical analysis. Furthermore, the lower slope of the V O 2 ϫ Q TOT (Ca O 2 ) relationship (values ranged from 0.6 to 0.8) is explained to a large degree by the much wider range in [Hb] and FI O 2 in the present study compared with the conditions studied by Ferretti et al (5).…”

“…Recently, Ferretti et al (5) have further developed the idea that Ca O 2 and blood flow are regulated to maintain a fixed femoral Cv O 2 or mixed venous Cv O 2 at a given exercise level. In the present study, with cardiac output measured by dye dilution and direct measurement of femoral Cv O 2 , we were not able to verify a constancy of Q TOT ϫ Cv O 2 .…”

Partitioning locomotor energy use among and within muscles Muscle blood flow as a measure of muscle oxygen consumption

“…In interpreting the correlation between muscle blood flow and V O 2, one should bear in mind that the regulated variable in the microcirculation of skeletal muscle is oxygen delivery, not blood flow per se (Rowell et al, 1986;Ferretti et al, 1992;Koskolou et al, 1997;Gonzalez-Alonso et al, 2006). Thus, the relation between muscle blood flow and V O 2 is dependent on the carrying capacity of the arterial blood, the saturation of hemoglobin with oxygen, and the oxygen extraction efficiency.…”

Introductory and Historical Remarks

“…A better understanding of the cardiovascular responses to exercise was made possible by the obtention of beat-by-beat recordings of arterial blood pressure and cardiac output. New concepts were created, such as that of phase III or slow component of the _ V O 2 response to exercise (Gaesser and Poole 1996) or of oxygen flow in mixed venous blood (Ferretti et al 1992). The technical developments in single fibre muscle physiology, and in molecular biology, led to deeply investigate the molecular functional characteristics of muscle diversity (Bottinelli 2001;Cerretelli and Gelfi 2011;Schiaffino and Reggiani 2011).…”

“…The x-axis intercept indicates the temperature at which E = 0 kJ, which was defined as the absolute zero. Taken from Ferretti and Capelli (2008) was called the absolute zero. When Lord William Kelvin (1824Kelvin ( -1907 set this temperature equal to zero-in practice, in Fig.…”