Maximal Oxygen Uptake Relative to Plasma Volume Expansion

Abstract

Controversy exists as to whether plasma volume (PV) expansion has the potential to increase maximal oxygen uptake (VO2max). In the present study, VO2max and exercise time to fatigue were measured in nine untrained men when plasma volume (PV) was normal and then again on the next day following two levels of PV expansion. Resting PV was expanded (via intravenous infusion of a 6% dextran solution) by 282 +/- 16 ml (i.e., PVX-1) and then by 624 +/- 26 ml (i.e., PVX-2). PVX-1 increased stroke volume (CO2 rebreathing) during submaximal exercise by 15% (P less than 0.05) above normal levels. VO2max following PVX-1 was increased 4% (P less than 0.05; 3.78 to 3.92 l/min) despite a 4% reduction in hemoglobin concentration. Exercise time to fatigue was also increased (P less than 0.05). PVX-2 resulted in an 11% (P less than 0.05) reduction in hemoglobin concentration during maximal exercise and a return of VO2max and exercise time to normal levels. In summary, we have observed in untrained men that 200-300 ml of PV expansion increases SV, measured during submaximal exercise, yet causes only a small amount of hemodilution. As a result, VO2max is increased slightly and performance is improved. Further PV expansion to levels 500-600 ml above normal results in an excessive hemodilution and a subsequent decline in VO2max and performance to normal levels. There is an optimal PV for eliciting VO2max in untrained men which appears to be approximately 200-300 ml above their normal levels.

Changes in Exercise Cardiac Function With Age in Endurance-Trained Females

“…These authors postulated rhat ET athletes may already be at an optimal BV which is at the limit of their diastolic reserve capacity. In agreement, other uivestigators have proposed that a diastolic reserve capacity exists and is recruited in response to optimal increases in BV, beyond which no further inatmes in SV willoccur in either ET or NA individuals (45,128). Since physiological LV hypemophy has been associated with improved indices of diastolic f i h g at rest and during exercise in both younger and older ET males (33,62,72,79,85,167), it is possible that this mechanism may be partiy responsible for setting the upper limit of diastolic reserve capacity.…”

Postural differences in hemodynamics and diastolic function in healthy older men

“…However, the lack of an increase in early diastolic Wlling volume in the study by Downes et al (1990) and the fact that changes in stroke volume were attenuated in both studies may indicate that diastolic properties limit the increase in stroke volume in healthy older men. Gledhill et al (1999) and others (Coyle et al 1990;Krip et al 1997;Martino et al 2002) postulate that blood volume is the major determinant of stroke volume reserve in young healthy men. Aging is associated with a reduction in total blood volume (Davy and Seals 1994), thus it is possible that supine posture caused less of an increase in left ventricular preload in the older men in this study.…”

Influence of High-Intensity Interval Training on Adaptations in Well-Trained Cyclists

“…These adaptations have been reported to increase both V O 2 max and exercise time to fatigue by 4 and 11%, respectively, in untrained individuals (3). However, well-trained athletes already have a high PV (32), and although PV can be artificially increased in these individuals (31), whether this plays a role in improving stroke volume, V O 2 max, and/or performance remains equivocal (26,31,32).…”