Maximal Aerobic Power
A high maximal aerobic power (or maximal oxygen uptake, V̇O2max) is important to succeed in athletic events requiring sustained activity at high metabolic rates; therefore, V̇O2max increases often translate into improved athletic performance. V̇O2max is defined as the maximal rate at which oxygen is being utilized by body tissues during physical exercise and is dependent upon both central circulatory (oxygen delivery) and peripheral (oxygen extraction) factors. Oxygen delivery to working muscles is a function of muscle blood flow and oxygen content of blood. If blood doping increases hemoglobin concentration then oxygen content will increase, as each gram of hemoglobin carries about 1.34 ml of oxygen, and oxygen delivery will be increased providing that blood flow is not correspondingly decreased.
Investigators who infused the RBC product of 2 blood units reportedV̇O2max increases of 4%-11%.[9,11,14,43,50,52,59,62,64] Investigators who infused the RBC product of 3–5 blood units reported that infusion of the second through fifth units produced additional increases inV̇O2max.[14,59] Numerous studies have demonstrated that EPO administration will markedly increase V̇O2max of anemic hemodialysis patients.[3,27,32,36,47] RBC infusion and EPO administration, however, seem to provide similar ergogenic effects for a given increase of hemoglobin in healthy persons.
Investigators[32,36,46,56] report that the relationship between changes in hemoglobin/hematocrit and changes in V̇O2max after blood doping are strong with group analyses, but do not hold well with individual subject analyses. Therefore, it appears that a person's ergogenic response to blood doping might depend on a variety of physiologic factors such as genetics, fitness level, and training state.
When V̇O2max is increased following blood doping, a given absolute power output represents a lower percentage of the newV̇O2max (lower relative power output). For example, in one study the power output representing 91% of the predoping V̇O2max was only 87% and 85% of the new V̇O2max values following the reinfusion of RBC from 2 and 3 blood units, respectively. Consequently, many investigations report unchanged V̇2, lower heart rates, lower venous and arterial lactate, and higher venous and arterial pH values at a standardized submaximal power output following blood doping.[11,14,19,20,43,45,59] This reduced physiologic strain should contribute to improved submaximal performance after blood doping.
Numerous laboratory tests have been used to assess blood doping effects on submaximal performance. For highly trained male runners, RBC infusion improved run time to exhaustion at 95% of the preinfusion V̇O2max by 20% and 34% (control run, ≈7 min) at 24 h and 7 d, respectively Another group of well trained male distance runners improved their 5-mile treadmill run times by ≈2% after RBC infusion, with most of the reductions occurring in the final 2 miles. Trained male mountain climbers demonstrated a 16% increase in treadmill run time during a multistage test after RBC infusion. Untrained men ran on a treadmill 13% longer at the same%V̇O2max (≈67% pre- and post-) after RBC infusion. For active women, time to exhaustion increased by 19%-26% during a progressive cycle ergometer test after RBC infusion.
EPO administration improved run time to exhaustion by 17% during a progressive treadmill test in recreationally trained men. Likewise, investigations have shown that EPO administration to anemic adults and children with renal disease increases their physical work capacity by ≈10%-100%.[3,7,12,15,27,34,36,47]
Studies examining the effectiveness of blood doping on race performance have consistently reported improvements, primarily in the distance as opposed to shorter events. For trained distance runners, RBC infusion decreased 3-mile run time by ≈24 s, and a sham reinfusion had no effect. For cross-country skiers (single-blind design), 15-km race times decreased by 5% and 3% at 3 h and 14 d post-infusion, respectively. For male distance runners (double-blind design), 10-km run times decreased by 69 s after RBC infusion. In another study (double-blind design), the same investigators found that RBC infusion decreased 1500-m run time on a track by≈5 s. In both studies sham infusions had no effect on race time.
Recently, an analysis of cumulative improvement in run time after RBC reinfusion (product of 2 blood units) as a function of race distance was performed. The data used in the analysis were derived from the one laboratory and three field studies cited above where male subjects participated in running races over distances of 1500 m to 10 km. The cumulative post-reinfusion improvement in run time increased as a function of the completed distance, such that predicted run times improved ≈7, ≈30, and ≈68 s at distances of 2, 6, and 10 km, respectively.
Cite this: ACSM Position Stand: The Use of Blood Doping as an Ergogenic Aid - Medscape - Oct 01, 1996.