Received November 21, 2005
Revised December 19, 2005
Accepted after revision January 17, 2006
Human, Environmental & Exercise [250]
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Influence of blood donation on Vo2 on-kinetics, Vo2 peak, and time to exhaustion during severe-intensity cycle exercise
Mark Burnley 1,
Claire L Roberts 2,
Rhys Thatcher 1,
Jo H Doust 1,
Andrew M Jones 3*
1 University of Wales Aberystwyth
2 Manchester Metropolitan University
3 University of Exeter
* To whom correspondence should be addressed. E-mail: a.m.jones{at}exeter.ac.uk.
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Abstract |
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We hypothesised that the reduction of O2-carrying capacity caused by the withdrawal of ~ 450 mL blood would result in slower Phase II O2 uptake (Vo2) kinetics, a lower Vo2 peak, and a reduced time to exhaustion during severe-intensity cycle exercise. Eleven healthy subjects (mean ± S.D. age 23 ± 6 years, body mass 77.2 ± 11.0 kg) completed 'step' exercise tests from unloaded cycling to a severe-intensity work rate (80 % of the difference between the pre-determined gas exchange threshold and the Vo2 peak) on two occasions before, and 24-hours following, the voluntary donation of ~ 450 mL blood. O2 uptake was measured breath-by-breath and Vo2 kinetics estimated using non-linear regression techniques. The blood withdrawal resulted in a significant reduction in haemoglobin concentration (PRE: 15.4 ± 0.9 vs. POST: 14.7 ± 1.3 g·dL-1; 95 % confidence limits (CL): -0.04, -1.38) and haematocrit (PRE: 44 ± 2 vs. POST: 41 ± 3 %; 95 % CL: -1.3, -5.1). Compared to the control condition, blood withdrawal resulted in significant reductions in Vo2 peak (PRE: 3.79 0.64 vs. POST: 3.64 0.61 Lmin-1; 95 % CL: -0.04, -0.27) and time to exhaustion (PRE: 375 129 vs. 321 99 s; 95 % CL: -24, -85). However, the kinetic parameters of the fundamental Vo2 response, including the Phase II time constant (PRE: 29 ±8 vs. POST: 30 ± 6 s; 95 % CL: 5, -3), were not altered by blood withdrawal. The size of the Vo2 slow component was significantly reduced following blood donation due to the lower Vo2 peak attained. We conclude that a reduction in blood O2-carrying capacity, achieved through the withdrawal of ~ 450 mL blood, results in a significant reduction in Vo2 peak and exercise tolerance but has no effect on the fundamental phase of the Vo2 on-kinetics during severe-intensity exercise.
Key Words:
Exercise, Oxygen, Respiration
