- 4.7% is the increase in mean power (W); No indication (in the abstract) regarding the time or distance or intensity of the 650 kcal time trials.
- No indication (in the abstract) regarding how much 4.7% increase on power impacts time trials of fixed distance measured by time, but the article from the journalist said 1 minute over 40 minutes, or 2.5% of time improvement.
- 650 kcal time trial initially looked like an odd choice of time trial - it was not obvious to me approximately how long such a time trial is. But after some thought, why not?
- a quick check and I found "On average, a 180 lb. cyclist riding at a moderate effort level will burn approximately 650 calories per hour", and it can vary based on weight and intensity
- not important, but 135/450 is 30%, and 235/450 is ~52%.
- One often proposed mechanism in these threads with respect to EPO studies with multiple injections over many weeks, is that the EPO allowed higher training load in the buildup to the race, (and indeed is better used in the off-season during aerobic buildup) rather than providing a direct effect on the race itself. In this study (assuming adequate wash-out periods) the time trials are just before and just after the blood transfusions -- making clear that the improved power is a direct result of the extra red blood cells, rather than a result of improved fitness due to weeks of a higher training load enabled by the blood transfusions.
Abstracts R us wrote:
This study tested the hypothesis that autologous blood transfusion (ABT) of ~50% of the red blood cells (RBCs) from a standard 450 ml phlebotomy would increase mean power in a cycling time trial. Additionally, the study investigated whether further ABT of RBCs obtained from another 450 ml phlebotomy would increase repeated cycling sprint ability.
In a randomized, double-blind, placebo-controlled crossover design (3-month wash-out), nine highly trained male subjects donated two 450 ml blood bags each (BT-trial) or were sham phlebotomized (PLA-trial). Four weeks later, a 650 kcal time trial (n=7) was performed three days before and 2 h after receiving either ~50% (135 ml) of the RBCs or a sham transfusion. On the following day, transfusion of RBCs (235 ml) from the second donation or sham transfusion was completed. A 4×30 s all-out cycling sprint interspersed by 4 min of recovery was performed six days before and three days after the second ABT (n=9).
The mean power was increased in time trials from before to after transfusion (P lt 0.05) in BT (213±35 vs. 223±38 W; mean±SD) but not in PLA (223±42 vs. 224±46 W). In contrast, the mean power output across the four 30 s sprint bouts remained similar in BT (639±35 vs. 644±26 W) and PLA (638±43 vs. 639±25 W).
ABT of only ~135 ml of RBCs is sufficient to increase mean power in a 650 kcal cycling time trial by ~5% in highly trained men. In contrast, a combined high-volume transfusion of ~135 and ~235 ml of RBCs does not alter 4×30 s all-out cycling performance interspersed with 4 min of recovery.