Sammy Izdatyev is the pen name of a Finnish sports enthusiast and unaffiliated amateur historian, who has been interested in endurance sports since the turn of the millennium. He hopes that his pro bono – research can provide more information into the body of literature of earlier underresearched areas of the history of sports.
Part IV: “The Breakthrough” (1969-)
The functional importance of the heart in the performance context was illustrated as early as 1897 when famous Swedish doctor Salomon Henschen estimated in one canonical study the heart sizes of ski racers before races using rather primitive techniques. When he compared the findings to the race results, they correlated strikingly well. Henschen thus concluded that “skiing causes an enlargement of the heart and that this enlarged heart can perform more work than the normal heart. There is, therefore, a physiological enlargement of the heart due to athletic activity: the athlete’s heart.” (Astrand, 1991)
Henschen had only speculated about athletes’ hearts being affected by training, but more than three decades later in the 1930s, it was observed that regular training lowered heart rate at a fixed work rate. That indicated that the amount of blood pumped and oxygen delivered with each heartbeat was larger, and correspondingly, a lower heart rate could keep the oxygen demand sufficient. And the implication was that there were extra reserves to be utilized when heart put ”all-in” when compared to the pre-trained level. (Saltin & Strange, 1992)
The México Olympics went well compared to the preceding panic about the possible health hazards and when endurance running events were dominated by African runners, one of the triumphant endurance athletes was cyclist Gösta Pettersson, who had been tested by Ekblom and his Norwegian co-author Lars Hermansen at the GIH. Whereas maximal oxygen uptake tests had been conducted on elite-level athletes, their cardiovascular system had remained a mystery until researchers began investigating the magnitude of how these athletes’ hearts adapted to training. The results were surprising. (Ekblom & Hermansen, 1968)
The first discovery was that the athletes’ hemoglobin concentrations were borderline anemic compared to “normal” clinical reference values. Gösta Pettersson’s hemoglobin concentration was only 13.4 g/dl, and one male orienteer had an even lower number, 12.8 g/dl, which equaled hematocrit values around 40 percent and 38 percent, respectively. The strangest part was that their maximal oxygen uptakes were still very high and this was explained by the enormous amount of blood their heart pumped every minute. The highest figures Ekblom and Hermansen measured were so high that they re-tested the athlete to make sure they hadn’t made an error. The figures came back the same, but the highest cardiac-output figure was still too high to be believed by Ekblom’s colleagues.
“They thought it was wrong, that we had measured it wrong in some way,” he reflected. “It was impossible for the heart to beat three times a second and put out some 200 to 220 milliliters per stroke.”
The research emphasized the importance of cardiovascular adaptation and tilted heavily to the validity of the “central” theory. When one Swedish journalist visited the GIH in 1969 to write about the laboratory, Ekblom mentioned the low hemoglobin concentration as an interesting phenomenon. The journalist speculated that it might be explained by iron deficiency, but Ekblom had a different opinion.
“Even though the values are clearly lower than usual for healthy people in their 20’s, I do not think these athletes suffer from iron deficiency,” he said, explaining that lower hemoglobin concentrations can be considered a normal adaptation mechanism of the well-trained body rather than anemia. (Olson, 1969)
In the midst of the blood-reinfusion studies, Ekblom obtained data that the human body aims to dilute the blood and that some well-trained athletes can have borderline anemic hemoglobin concentrations. He didn’t consider this any “real” form of anemia, but rather a natural and possibly a beneficial reaction to regular training. Ekblom still considered the theory behind the blood doping to be sound since earlier research had given some positive results.
One item from unpublished blood-doping research found its way into this paper, as Ekblom and Hermansen noted former’s “unpublished observations” on cardiac output being elevated after blood donation, when the amount of blood was recovered but diluted. That is to say, the heart partially compensates for the loss of blood-oxygen carrying capacity by increasing blood flow above a normal level. The observations were made during one inconclusive blood-doping experiment.
Nothing had yet been published about blood doping, and if a sharp-eyed reader of the Journal of Applied Physiology wondered why Ekblom had removed the blood of his subjects, he or she would find the answer a few years later from pages of the same peer-reviewed journal.
A new attempt
After a few dead-end blood doping attempts with inconclusive results, in 1970, Ekblom took another attempt on the subject in 1970 coauthoring another paper on the subject with Dr. Alberto N. Goldbarg, who was an MD and on leave from the Department of Medicine (cardiology) of the University of Chicago. (Ekblom et al, 1972a)
While most people today, doping specialists included, are unaware of the preceding attempts to test the blood-doping hypothesis from the 1960s, there is a great deal of data available about this study since the detailed report was published in a prestigious journal.
Blood infusion was now tested with two experimental groups, with significantly higher amounts of blood than was earlier used. Group I donated 800 milliliters blood that was reinfused 28 days later, whereas Group II donated 400 milliliters of blood three times at four-day intervals, totaling 1200 milliliters, and had the blood reinfused 32 days after the first donation. Ekblom said there hadn’t been a complex thought process regarding the storage period and amount reinfused, and by chance, they ended up with this protocol. Various blood and endurance parameters were monitored during the research. The key endurance test was the time to exhaustion, requiring the subjects to run as long as they could, and maximal oxygen uptake was also measured.
As expected, both maximal oxygen uptake and maximal working time both fell significantly after blood donation. Hemoglobin concentration decreased by about 13 percent in Group I and 18 percent in Group II, and their treadmill-running endurance also collectively decreased by a third. Bone marrow quickly began increasing red-blood-cell production, and when the blood stored at 4 degrees Celsius was infused four weeks later, there was an “overnight” improvement both in endurance time and in VO2max in the Group I. The authors noted the participants’ sudden 9 percent increase in VO2max and ability to run 23 percent longer on a treadmill.
This is the blood-doping effect that shocked the world. Actual day-to-day competition remained vastly different than time-to-exhaustion while running, and it should be emphasized that the 23 percent improvement in the maximal working time in that treadmill test describes how much longer an athlete could run at given speed, rather than how much their speed could be increased at a given distance. The improvement in speed wouldn’t be of the same magnitude, and Ekblom himself told the Swedish media that steeplechaser Anders Gärderud could theoretically improve his 3000-meter steeplechase record by 10 seconds, and because his personal best (and the Swedish national record) at that time was 8:28.4, the “real” improvement in direct speed would be “only” 2 percent.
Even when 2-percent improvement in speed, as well as improvement in VO2max figures, sound tolerable, they would have a serious impact on performance for reasons Ekblom would describe a decade later.
“Firstly, it should be borne in mind that in sport the difference in performance between first and last, in a top-level event, may be only measurable in parts of a percent, which means that even very small changes in the different factors contributory to physical performance may be of vital importance,” Ekblom wrote in 1982 when putting the performance improvements in “real” context. “Secondly, increasing gross maximal aerobic power by 5 percent in an already well-trained athlete may be almost impossible, at least over a year or so.” (Ekblom, 1982)
One can deduct that researchers thought there would be other studies to follow and thus didn’t keep overly detailed data on the aforementioned study. There was also a chance the results wouldn’t be published at all. Even when one of the assumptions was to research the effect of elevating hemoglobin concentration on the other links, cardiac output wasn’t measured even when Ekblom was familiar with the procedure, having studied the cardiac systems of athletes a few years earlier with the Norwegian exercise physiologist Lars Hermansen. Yet at the time, Ekblom and Goldbarg were involved in other research projects regarding other links of the oxygen transport chain and in any case, their research lab resources were finite.*
Later, Ekblom went on to republish the data and figures on the 800 ml group, but the authors seemed unconvinced about the improvements in the 3×400 ml group, even when the improvement in the working time was similar. This led to a situation where there were only three subjects in the “main group”, which led to some anomalies. Goldbarg and Ekblom were surprised that maximal oxygen uptake had returned to the original level in 14 days, while hemoglobin concentration had barely risen from low “anemic” values and maximal work time was below the original level and hadn’t fully recovered even after 27 days just before the reinfusion. They had no explanation. Another interesting observation was that submaximal heart rate wasn’t lower after blood reinfusion, even when oxygen flow should have been sufficient at lower blood flow, i.e., lower heart rate.
There had also been no increase in VO2max in “Group 2”, where the reinfused amount was 3×400 ml of blood, even when total hemoglobin had been increased by some 10 percent. While the researchers concluded that the results were generally similar among the groups, that incremental protocol was rarely used again in testing. Additionally, when Ekblom described the research in detail in an article he wrote for the Swedish sports journal Svensk Idrott in 1972, he didn’t bother to mention the incremental group but focused solely on the 800 ml group and all the three subjects of this group also recalled their ”blood doping” research experiments later in various media outlets.
While now there was a blood reinfusion study with improvement, the study was heavily prone to criticism for a variety of reasons and not alone for the reason that there were very only a handful of subjects.
The most pertinent problem was that there was no ”real” control group because all the changes in the data were compared to earlier baseline values of the same people, which would lead to two types of future criticism. The first criticism was the placebo effect, when the participants might have known what the research was about and known not giving full effort after blood donation and perhaps an extra boost when they knew about the benefits of the extra red blood cells.
It has also been suggested that some training effect might have taken place, as the subjects gave their maximal effort on a treadmill on several occasions and their regular training protocol wasn’t monitored. Correspondingly it was possible that some changes in VO2max could have been explained simply by natural training adaptation and not in the change of hemoglobin concentration or total hemoglobin. Another criticism was how well the results could be extrapolated to elite-level athletes, an item that Ekblom recalled the media being more interested in than the scientific community:
You just take out some blood and give it back thirty days later that gives performance enhancement going from the last place in the race to the first. That has an enormous sport effect. That’s why the reinfusion of blood became so interesting in the media. That was not that much discussed in the scientific world as in the media. The effect of sports performance was, of course, something that the journalists found very interesting.
While the subjects of Ekblom and Goldbarg were fit medical students with relative VO2max figures ranging from 54.9 to 71.4 ml/kg/min, there was always doubt whether the method would work on international-level athletes who were following rigorous professional type training programs and had reached the natural limits of their VO2max. It might’ve also been that the actual ”limitation” in the oxygen delivery chain might be different than that of even national-level athletes.
While both Ekblom and Åstrand voiced concerns about the doping aspect publicly in the 1970s, considering it very likely that the method would also benefit elite-level athletes, they didn’t specifically touch the issue in their papers.
“Research surrounded by secrecy”
In September 1971, some Swedish newspapers got tipped off about the ongoing research and contacted Ekblom and Åstrand for comments. (Carlsson, 1971a) Åstrand declined to comment, and Ekblom wasn’t that talkative and told the media that “it will be just a lot of sensational writing” because “it is a matter of medical expertise that really understands what we do” and therefore there was “nothing for sports journalist”. That prompted a sports journalist from Aftonbladet to write that their research was “surrounded by a lot of secrecy”. That journalist knew also that there were two attempts, of which only one gave clear benefits and the other was more inconclusive. He also knew that there were two physiologists involved, but his assumption that Ekblom’s coauthor was Åstrand indicated that he wasn’t that fully aware of the details. Goldbarg wasn’t mentioned in the news despite being the coauthor of perhaps the most significant blood-doping research paper, which confirmed that the research wasn’t Swedish “inside business”. In fact, foreigners coauthored even unpublished research. To this day, Ekblom refutes the secrecy claim as he discussed some items in his lectures, even when the material wasn’t published anywhere:
A lot of people knew about it. There were roughly 25 students in two parallels each year, so fifty per year, if the were on the lectures, of course. We have had so many subjects also, they knew the effect. In the late 1968 or 1969, I had lectures at the GIH for the students and I presented them some of the results before we had published anything in the publication.*
*A Swedish correspondent of Track and Field News also easily found a Swedish student who was familiar with the research and knew it in detail and gave some comments on the subject matter. (Track and Field News, 1971)
While the researchers didn’t comment on the subject publicly while the research was ongoing, it wasn’t necessarily a secret considering the first attempt was revealed at the 1966 meeting of the Scandinavian Physiological Society in with a brief mention in its journal Acta Physiologica Scandinavica. Additionally, the prestigious peer-reviewed Journal of Applied Physiology had accepted the manuscript for publication two months earlier, therefore the “secrecy” would have been unsealed relatively quickly, in some 10 to 11 months.
Ekblom nevertheless gave a more detailed account to journalist Omar Magnergård of the large newspaper Svenska Dagbladet, whom he was in friendly terms with, and the resulting article was a deep look into the subject headlined: “perfect doping”. Ekblom described the key technical details of the research, such as the time between blood removal and reinfusion, the amount of blood reinfused, as well as the performance enhancement. He also stated that the test subjects were GIH student-athletes, including some football and basketball players and even one of Ekblom’s orienteering teammates. (Magnergård, 1971)
Magnergård observed that there had been no control group, but it didn’t automatically invalidate the results, far from it. “Critical voices can disagree, that psychological or other factors have been played and partly caused the increase. Björn Ekblom agrees with this reasoning.”, noticed the journalist correctly one possible criticism of the findings. “However, no such a thing can affect the oxygen uptake capacity. And it increased by nine percent!”. (Magnergård, 1971)
Additionally, Ekblom emphasized that the participants didn’t know the goal of the research, only that they would run on a treadmill and have blood removed and reinfused, a view confirmed by one of the participants some 40 years later. ”It was very secretive,” Bengt Fredenlund – a national-level basketball player and one of the seven participants (all of which were GIH students) – also recalled. ”We didn’t know what we said yes to.” (Hansson, 2009)
One should also keep in mind that in 1970 there was no term blood doping and nobody knew how it would affect performance. It means also that it isn’t certain that the placebo effect existed that much when the subjects didn’t read too much into its known benefits, because there existed no known benefits, no literature, no sensational headlines, no succesful blood dopers to refer to.
While Ekblom and the journalists were concerned that the practice would spread into sports, Ekblom was also interested in whether the method could be used to treat other medical conditions in more ordinary health care. He wasn’t able to determine that, but said he felt he contributed a “small piece” to the puzzle of understanding the premises that have significance on the mechanisms of the human body.
Still, the sports issue troubled Ekblom very much, and he expressed that it would be undetectable. “To detect this type of doping is almost impossible,” he wrote in 1972 in an article titled, “Does blood doping become a sports problem?”. “Theoretically there would exist some possibilities for this, but it is not realistic in practical terms.” (Ekblom, 1972) He also states in the same article that blood doping would without doubt fit the definition of doping.
Blood doping was reported worldwide in various media outlets and some sports journals, such as Track & Field News, became interested in the topic and inquired the opinions of specialists on the subject matter. (Track and Field News, 1971) Dr. Ernst Jokl of the University of Kentucky had five years earlier told about South African runners who resided at the altitudes of Cape Town to gain more red blood cells with benefits. ”There has accumulated a great deal of evidence to show that considerable advantage results from living and training at an altitude of 6,000 feet, and if they wish to set new records, they go back to sea level to compete”, Jokl described the benefits of this technique in one Mexico-related international symposium in 1966. (Bynum, 1967)
Against this background, Jokl was surprisingly not convinced about blood doping hypothesis. ”It is probably worthless but it may be appropriate to inquire from Prof. P.O. Astrand what all the noise is about”, Jokl told the T&F News correspondent.*
*Historian John Gleaves writes in his essay about the cycling blood doping scandal of the 1984 summer olympics that this article ”brought the scientific debate over the benefits of blood transfusions to a North American audience of athlete and coaches interested in improving running performances” (Gleaves, 2015). Ekblom’s view was that the issue became ”of worldwide interest” only some five years later after the 1976 Summer Olympics (Ekblom 1982). Gleaves doesn’t find that much blood doping-related media material preceding the 1976.
Not all were as dismissive as Jokl was.
“The Swedes are perhaps the most advanced nation in the study of exercise physiology,” commented Olympic running coach Jack Daniels, who studied in Sweden and knew the GIH researchers. “If Ekblom actually did the work, I have no reason to doubt the results – if reported correctly.”
Ekblom clarified his research to Daniels in a letter quoted by T&F News, clarifying the purpose of the research pointing out that the goal ”was not to find a perfect way of doping athletes but to study the different parameters that will influence the oxygen transport system chain and general physical performance” even when ”the study has become of greatest interest to coaches and trainers all over the world”. While some sports people contacted him, Ekblom recalls that there were surprisingly few exercise physiologists who contacted him directly and more (but not much) interest came from people who wanted to take advantage of his method:
One of the first questions I had was that if this type of manipulation could be done on race horses and dogs, which is strange that it was not the sport people that called.
Ekblom revealed to the American journal that he was offered 100,000 Swedish Krona ($20,000 U.S. dollars) for the exact method, an offer he refused. One journalist later claimed that this offer was made by a professional cycling team in order to help them with the procedure. (Byström, 1981) ”That is right and as a poor father of two children it would’ve been tempting, but I understood the consequences – I would’ve lost my credibility in the future”, Ekblom recalls today.
While the few opinions about the validity of Ekblom’s research were diverging within the community of exercise physiologists, still one specialist of his own arena thought he knew better:
There was a professor of cardiology who said: ‘You must have made something wrong; this is not possible. The viscosity will increase and you will have reduced circulatory performance during heavy exercise’.
That sentence would set the tone of the discussion for the next decade to come.
Meanwhile, research on manipulation of the other links continued, and two additional studies coauthored by Ekblom were published in 1972. One dealt with “blocking” a portion of hemoglobin by inhaling carbon monoxide, which had higher affinity to hemoglobin than oxygen. Unsurprisingly VO2max and performance fell significantly when a large amount of RBCs were rendered unusable.
Another interesting venue was limiting maximal heart rate by administering two beta blocker – substances: atropine and propranolol to hinder heart function and to keep hear rate artificially low. When the body couldn’t increase oxygen flow to muscles by increasing heart rate even when muscles had a high demand for oxygen, there were two compensatory mechanisms. The body increased the stroke volume above earlier presumed “maximal” levels and it also increased the relative amount of oxygen used by the muscles.
Correspondingly, maximal oxygen uptake was lowered by just 6 percent, which was statistically negligible. One could deduct that this showed the body’s enormous capabilities when it adapted if one link was manipulated down. Another plausible scenario was that central circulation wasn’t the key limiting factor or at least not the end of the story about what limits Vo2Max.
Part V: “Too simple trick”
The media interest in the autumn of 1971 triggered more than just public discussion and ranging opinions. Some interested parties attempted to replicate the findings before they were published in full detail in August 1972, using bits and pieces of what they could extract from news reports.At least two attempts took place before the study was published. The first published attempt took place in late autumn of 1971, a few months before the 1972 Sapporo Winter Olympics, when a doctor with the Finnish Ski Federation and future member of the International Ski Federation (FIS) Medical Committee, Tapio Videman, and his colleague Tapio Rytömaa tried to determine whether blood doping enhanced performance by testing reinfusion on 10 recreational-level cross-country skiers (Videman was one of them) taking out between 400 and 600 millilitres of blood and reinfusing it back 14-21 days later. The only performance-related item measured was submaximal heart rate, and while Videman and Rytömaa observed some benefits in performance after reinfusion (slightly lower submaximal heart rate), the enhancement wasn’t statistically significant and could have been explained by training effect. (Videman & Rytömaa, 1977)
In light of the later revelations about the blood-doping use in the ’70s, it is interesting that this finding was reported to the Finnish Olympic Committee and some MDs later recalled having participated in a meeting where blood doping was discussed and shown to have been ineffective. The Videman-Rytömaa research paper was published only in 1977, over six years after the research.*
*After blood doping was debated in the Finnish television in November 1972 –, shortly after the ’72 Olympic games – and concerned doctors claimed that the use was rampant, this study was mentioned in passing when the officials denied the efficacy of the method. ”Recently a known blood specialist Tapio RytoÅNmaa gave a statement in a meeting of sports MDs and coaches telling that transfusion has no benefit for a normal person or an athlete”, the training chief of the Finnish Olympic Committee told in one interview. ”Why on earth would transfusions be used in sports, if they are of no benefit whatsoever?” (Vaasa, 1972)
Only a few months later, exercise-physiology student Jerald Bocrie at Old Dominion University in Virginia showed professor Melvin H. Williams the Track & Field News article about the blood-doping research. Williams was heavily interested in physiology being the head coach of the cross-country team of the university and Bocrie was the assistant coach. He also deeply respected the Swedes and felt their reinfusion-hypothesis was intuitively logical knowing also that the GIH had a good reputation, considering Åstrand coauthored the famous Textbook of Work Physiology with Kaare Rodahl:
Sweden was the place to study, and many of the top exercise physiologists in the United States did so. I admired Dr. Åstrand, and used his textbook to teach my graduate exercise physiology class. I met him at several American College of Sports Medicine meetings over the years. He was the pioneer of exercise physiology. I would have liked to have studied in Sweden after my doctorate, but was not aware of their program at the time.*
*Some remarks made by Melvin H. Williams (1938-2016) with no reference are based on our email-correspondence that took place in 2014.
Williams and the student decided to conduct a study to find out whether the theory worked by using runners from a local club as their subjects teaming up with two other researchers to solve the mystery of blood doping. They placed the runners into four groups, where each component of blood was tested in isolation. Knowing that exercise increased the amount of plasma, Williams and the student were interested in how exercise would be affected when only plasma was infused, without the red blood cells. (Williams et al, 1973)
They measured submaximal heart rates and time to exhaustion and observed minor but mostly inconsistent declines in heart rates in every group, an effect that was most evident in the “whole blood” group. Still, their statistical analysis revealed no differences between the four groups, and correspondingly, Williams and his coauthors concluded that with the limitations of the study, blood doping didn’t work.
Thus the first two published attempts taking place outside Sweden to test the underlying theory behind the Swedish researchers’ blood-doping hypothesis failed. Ekblom continued to focus mostly on his own work and avoided confrontation in dealing with skepticism. Still a decade later he wrote that “some very serious mistakes occurred in these studies”, (Ekblom, 1982) and if he had seen the test protocols beforehand, he likely would have predicted the outcome since he had firsthand information about similar mistakes made a few years earlier. “We had done exactly the same mistakes in our own pilot studies in the late 1960s”, he thinks about the obvious similarities.
In addition to using only half the amount of blood and reinfusing it back in only 21 days, a week earlier than Ekblom and Goldbarg had, one of the mistakes was that the authors of the Williams et al study didn’t gather any hematological data, so in hindsight it isn’t certain that there was an increase in hemoglobin concentration at all. Still, Williams and his co-authors appear to have been sincere and honestly confused and surprised about the findings spending a full third of the research paper on various possible reasons to explain why the method didn’t work. They notice a similarity between high altitude studies with inconclusive results. ”These findings may be analogous to studies which have shown that polycythemia associated with training at altitude exerts no beneficial effect on maximal oxygen uptake or performance on subsequent return to sea level”.
The Finnish findings can also be explained by the same problem because the amount of blood reinfused in the Finnish research was only 400-600 milliliters – only half of what Ekblom and Goldbard had used – and the research paper is strikingly similar with the earliest inconclusive tests. The authors didn’t find significant performance enhancement even when they concluded correctly that the ”prerequisite for a possible benefit from autotransfusion is that hemoglobin level and [hematocrit] recover sufficiently within 2 to 3 weeks”. Their study didn’t meet this condition and the volunteers were clearly anemic when the reinfusion took place, hematocrit being almost the same before blood removal (42.2 %) and after reinfusion (43.3 %).
Melvin Williams met Åstrand in many conferences and Tapio Videman visited the GIH at least once (in March 1973) with the best Finnish cross-country skiers, when the 6”5 skier Juha Mieto broke the absolute Vo2Max world record with gigantic his oxygen engine of 7.40 l/min when he was tested by Bengt Saltin. Unfortunately, Ekblom can’t recall what types of discussions took place about the subject-of-the day.
“Whether Melvin – whom I knew well – or Videman discussed the matter with us when they visited the GIH, I don’t remember, but it is likely that we did, particularly when it was P-O Åstrand who initiated visits and discussions on various subjects”, Ekblom recalls.
While the published blood doping research was scarce in number in the years following immediately the 1972 study, Ekblom believes that people started to make their own ”underground” experiments with blood reinfusion almost right after his study was published. As one interesting anecdote, Björn Ekblom recalls how a member of the Soviet embassy in Sweden contacted his lab and wanted to see the testing premises and discuss the matter. Afterward,d it didn’t seem so good idea even when he told him everything that he had told everybody else interested in the matter. After the fall of the Soviet Union, it was revealed that blood reinfusion research started in the country in the mid-1970s. (Kalinski, 2003)
In any case, the research was available for everyone interested and who bothered to visit the nearest university library to pick up a copy of the journal and read it for themselves.*
*Track and Field News affiliate quarterly journal Track Technique also published a detailed account of the 1972 study in 1973 titled ”Blood Boosting: Its effects on Exercise”. (Track Technique, 1973)
Fundamental vs. practical research
If many of the so-called ”real” physiologists and medical doctors had looked down on exercise physiologists and the research undertaken at the GIH because they didn’t do ”real” worthwhile science, the opposition that came from within sport circles was of an almost totally different type of nature.
When the cooperation between the Swedish Ski Federation and GIH started in the mid-1950’s, some skiers felt that they didn’t want to be subjected to ”scientific” training. Two Swedish historians wrote that ”many of the skiers were hesitant or even hostile to this scientific turn. They felt that their own expertise was undermined, that they were reduced to guinea pigs in the lab and that they did not get sufficient explanation of the test procedures, results and how to use them in their own training”. (Svensson & Sörlin, 2018)
Björn Ekblom also noticed two decades later that the attitude of coaches wasn’t that better when with Per-Olof Åstrand he explained the research conducted at the GIH to one journalist who was visiting the institute.
“There does exist an aversion of many sports bosses and coaches to physiologists. We are often accused of being only theorist. Therefore, I think it’s good that we have this contact with the actual sport. In addition, what we are dealing with here at the institution is in large part applicable directly to sports”, he explained. (Almgren, 1970)
The key area of improvement would be individual training programs and Ekblom considered the ”one-size-fits-all” training papers worthless and while a football enthusiast and a coach himself, he even preferred individual exercise to a large extent as time-saving when compared to group training that took up to three hours at a time.
Perhaps a clear majority of the research conducted at the GIH was still the so-called fundamental type of research which was barely comprehensible for sport enthusiasts even with above average knowledge on physiology in which the connection between research and application was everything but obvious. While blood doping was in its core fundamental type of research, it still was in the gray area of research, because the blood doping research was quickly dubbed simply ”GIH-method” when everyone understood right away that implications of the knowledge it provided and wondered how much this ”in large part applicable” blood doping know-how had been offered to the Swedish athletes. And how come the Journal of Applied Physiology that published the research has the name ”applied” in its name?*
*Finnish steeplechaser Jouko Kuha most likely wasn’t alone with his reading of the implications of the study with his 1971 remarks. ”The information from Sweden was so unbelievable thing that it made me laugh even a long time after I’d read it”, the earlier world record holder commented. ”If it was true that results would be bettered that much, you wouldn’t tell it publicly but you would take advantage of the method in secret”. (Raevuori, 1971)
An R&D research center of blood dopers?
In 1971, the Belgian cycling superstar Eddy Merckx was at the height of his career but skipped that year’s edition of the Tour of Italy. The Tour was subsequently won by Gösta Pettersson, who had been tested by Björn Ekblom and a participant of his study from the late 1960s that measured cardiac outputs. The physiologist commented on Pettersson’s physiology in the media when the cyclist had managed to become one of the few Swedes to compete at the international elite level in cycling. Pettersson complained regularly in 1970-1971 about his anemia and was infused with sugar solution and iron shots by the Italian team doctor of his Ferretti team, even when Ekblom hadn’t been that worried about the low hemoglobin concentrations as such of athletes with superior hearts.
One can only speculate what kind of thought went through the minds of his competitors when the existence of blood doping was revealed only a few months after his Tour of Italy win, but we do know that some French cyclists did ask Ekblom for assistance with the blood doping process and Pettersson’s main rival Eddy Merckx has later revealed that the Belgian was offered a possibility to use transfusion when the attempted to break the hour record in 1972.
What we do know is that later triumphant athletes from the Nordic countries wouldn’t be so lucky and the first ”real” target of blood doping accusations was found only shortly thereafter. Only shortly after blood doping became known as a method in fall of 1971, it was reported that 23-year old cross-country Sven-Åke Lundbäck recorded the highest relative oxygen uptake ever at the GIH laboratory, 87 ml/kg/min.
Lundbäck would be triumphant at the Sapporo Winter Olympics only months later by winning a gold medal in the 15-kilometer race by a 32-second margin, one of the largest in the history of Olympics and never surpassed since. Björn Ekblom commented about Lundbäck in various media outlets and the collaboration between the two was widely known and referred to in daily newspapers. Blood doping was also known as a method, and unsurprisingly a Swiss team doctor Hans Howald and the Norwegian team doctor Kjell Öystein Rökke recalled only a few years after the games that there were rumors about participants from the Nordic countries having taken advantage of transfusions (Howald, 1975; Dagbladet, 1978). The allegations remained still mostly unpublished until a Finnish biographer of endurance runner Lasse Viren claimed years later that many Finnish skiers were convinced that Lundbäck had indeed blood doped, complaining to their Finnish MDs and coaches that they wanted also access to the same arsenal of methods that the Swedes had. (Saari, 1979)*
*Dagens Nyheter journalist Bobby BystroÅNm questioned the claim about LundbaÅNck on the grounds there was no reason for LundbaÅNck not to triumph in the preceding major competitions (1974, 1976) if blood doping was a ”guaranteed way to medals” (BystroÅNm, 1980). The Finnish biographer of Viren also don’t believe in the LundbaÅNck-gossip in the actual book but considered that ”miracle method that everyone else certainly used” was only an easy way to explain one’s own bad success.
The discussion was very heated also in Sweden and already in 1971 steeplechaser Anders Gärderud mentioned in passing being interested in testing the method when the issue was the first time a news item. (Carlsson, 1971b) At the same time one journalist recalled hearing rumours that Swedish athletes had taken blood transfusion for the Mexico pre -Olympics (Olofsson, 1971) and a year later wrestler Pelle Svensson (world champion) named in his provocative book Öppet Brev Till Sveriges Idrottspampar in 1972 one Swedish swimmer by name as a ”guinea pig” of blood reinfusion experiments. (Svensson, 1973) Some media outlets claimed that the alleged physiologist of the latter experiment was none-other-than Bengt Saltin, and interestingly Svensson had been a participant of the Saltin’s 1965 high-altitude expedition (with some ten other athletes, among them cyclist Gösta ”Fåglum” Pettersson and steeplechaser Anders Gärderud) where Saltin had made some remarks about the use of blood transfusion as one option, so the people involved could’ve heard at least some speculation about the method.
The allegations were denied and after the issue had been debated in Swedish national television in 1973, Per-Olof Åstrand wrote even an open letter denying the allegations and specifically mentioned that the claim about Saltin was totally untrue, (Aslund, 1973) and the swimmer also denied later the claim. ”I never have doped, I trained hard”, he commented over two decades later the matter. (Bergfeldt, 1995). Pentathlete Björn Ferm – a participant of the pre-Olympics – also denied having ever heard that transfusions had taken place in Mexico, and Ekblom from his part denied that the method had been used at the 1968Olympicss. ”Overall the whole thing has been overblown”, he also commented how media got the research totally wrong. ”Some folks have deliberately misunderstood and distorted this topic. The method hasn’t been invented in order for athletes to enhance their performance”. (Olofsson, 1971)
Nevertheless, if the Swedes had a secret weapon, they had been unsurprisingly unsuccessful at the endurance events at the 1972 Summer Olympics. The development had been totally different in Finland, where there was a triumph after triumph that had started in 1968 when endurance runner Jouko Kuha broke the 3000m steeplechase world record after three mediocre decades. The success continued and three years later in 1971, Juha Väätäinen won both the 5000m and 10000m events at the European Championships in August 1971 and the success at the 1972 Summer Olympics was unbelievable with four medals – Lasse Viren (two golds), Pekka Vasala (gold) and Tapio Kantanen (bronze). When blood doping was mentioned as a research topic in September 1971 – only a month after the triumph of Väätäinen – Risto Taimi, the editor-in-chief of the largest Finnish sports journal Suomen Urheilulehti, wasn’t that certain that Ekblom had invented something totally new. ”This published research most likely isn’t a novelty inside the sports medicine circles of the world even when people haven’t kept that much noise about the topic”, he wrote, adding also that ”one can find clear evidence about the beneficial effects of this type of treatment, also from Finland”. (Taimi, 1971)
When blood doping was mentioned as a research topic in September 1971 – only a month after the triumph of VaÅNaÅNtaÅNinen – Risto Taimi, the editor-in-chief of the largest Finnish sports journal Suomen Urheilulehti, wasn’t that certain that Ekblom had invented something totally new. ”This published research most likely isn’t a novelty inside the sports medicine circles of the world even when people haven’t kept that much noise about the topic”, he wrote, adding also that ”one can find clear evidence about the beneficial effects of this type of treatment, also from Finland”. (Taimi, 1971)
When the editor-in-chief was asked about details by well-known journalist Antero Raevuori, he revealed that a competitor of Jouko Kuha had revealed to him that Kuha had been treated with a transfusion in 1968 for the world record run. The other incident he knew took place in 1970 when a well-known unnamed Finnish MD had told Risto Taimi that Juha Väätäinen had been also treated with a transfusion before he broke the 10,000m national record. (Raevuori, 1971) While the alleged incident took place a year before the 1971 games, a year after the games one Finnish doctor affiliated with the sports circles told knowing for certain that a number of Finnish runners had taken advantages of transfusion already for the 1971 European Championships, and Track & Field News correspondent Cordner Nelson recalled also having heard whispering about double gold medallist Väätäinen having used blood transfusions. (Nelson, 1972)
Väätäinen wasn’t available for the comments, but he was later dismissive about the benefits of blood doping and always maintained that ”naturally” obtained altitude red blood cells were the safest and best ones. While Jouko Kuha specifically denied the allegation, he mentioned having been familiar with the procedure and some other athletes, coaches physiologists told also that they knew that transfusions had taken place in Finland. MD Kaarlo Hartiala, the future Finnish member of the International Olympic Committee Medical Commission also told that the issue wasn’t totally new.” On a theoretical level, the subject has been known for a long time”, he remarked mysteriously. (Raevuori, 1971) Interestingly Tapio Videman – who had conducted the first known attempt outside GIH to research blood doping – also later recalled having heard ”amazingly sounding” rumors about athletes taking transfusions in the late 1960s. (Siukonen, 2001)
With all this evidence, there is an apparent mystery there – how could the method that was revealed in September 1971 be in use first time up to three years before that and how come the Finnish sports circles were aware of the method beforehand?
There are many possible answers to this question. Aside of the possibility that the Finns had invented the method on their own, they could’ve built upon the Swedish research having heard about the line of research, because dozens of Finnish exercise physiologists and sports MDs participated in the 1966 conference held in Finland where the first inconclusive results of Ekblom and Åstrand were discussed. Kaarlo Hartiala – who was the 1968 chief doctor of the Finnish summer Olympic team – also participated in the conference and was very well connected with the Swedish researchers relating to the high altitude adaptation research.
He was also the Finnish doctor of the 1965 expedition at the Mexico pre-Olympics with Bengt Saltin, so with his particular comments, he could’ve referred also to this line of research if the ways to take a shortcut to elevate hematocrit was discussed among the Nordic researchers. The third possibility was that his comments or the Finnish transfusions weren’t carried out at all to ”blood dope” but to treat relative anemia, a condition very common among the Finnish athletes. This was actually the consensus view of the rationale as told by the Finnish sportspeople who commented on the topic in 1971. In fact, Finnish athletes had been regularly complaining about their low hemoglobin counts and many had received iron shots with more-or-less success.*
*Finns also noticed the anemia recovery problem quite early on, already before the 1972 study was published. Dr. Pekeltokallio – a respected sports MD – speculated whether the body could’ve recovered ”via normal ways” from anemia in a month when the donated blood had to be reinfused (Raevuori, 1971) and Juha VaÅNaÅNtaÅNinen had a lot of substance in his comments. ”If one uses one’s own blood that has been stored earlier, the beneficial effect is questionable”, the European Champion commented the matter in November 1971. ”Human blood is a living substance, and today it isn’t possible to store it for a long time without some blood destruction taking place. After the blood has been stored for three weeks, some 30 % of the red blood cells. If the storage period is shorter, the human body hasn’t recovered the balance, ie. the amount of blood. Therefore one can’t gain anything by reinfusing the blood”. (Telaranta, 1971)
About what took place in Sweden, Björn Ekblom insists to this day that blood doping didn’t take place at GIH and that he wasn’t pressured to blood dope Swedish athletes, even when he doesn’t have a full picture about the prevalence of blood doping use at that time:
After my own experience [with blood reinfusion], I understood that this would be doping – no doubt about it. But how much this was used during the 60’s and early 70’s I do not know. How the accusations fell out during that time I do not remember – just that I denied all allegations that I and others Peo would’ve been involved in the matter.
He still revealed in an interview in 1975 to a Dagens Nyheter journalist that he had heard that a West German swimmer had broken the national record with the help of blood transfusion and he had information from his ”research colleagues” that the method had been used at a national level competition in a country he didn’t want them to reveal (Loren, 1975). Ekblom heard about the latter incident by an accident:
In one conversation I got confidential information – ‘ He went to a hospital to treat his anemia, but one doesn’t get three blood bags to treat anemia of a well-trained athlete’. The same argument has been used when athletes develop so-called ‘sports anemia’ and it must be taken care that he must have blood. After these newspaper comments I actually got some threats both from those who thought who he was and from those who had some questions to answer for.
The newspapers had called blood doping ”perfect doping” only a few years earlier, and Ekblom himself had been very skeptical about its detection possibilities, in fact, there had only been some speculation that elevated blood pressure might reveal blood dopers, but that the method was very insensitive because the normal range was so large. In this 1975 interview, Ekblom revealed that some thought process had still been going on also in this arena. ”The blood has an age range that can reveal if transfusion has occurred”, Ekblom speculated one possible method. ”When the blood is stored outside the body, the blood cells age at a different rate than those in the body” (Loren, 1975). While he described surprisingly accurately the future detection developments, he laments that very little was done in this area in the 1970s:
Our impression was that we could see the difference between frozen and fresh blood in the size of red blood cells, their age and perhaps from something else. We got the tip from a hematologist but didn’t proceed with this thing – pretty stupid from our part.
No Swedish athlete has ever admitted using ”old school” blood doping and Björn Ekblom has always consistently denied his own participation in blood doping. It still wasn’t listed as a banned method by the official rules and Ekblom recalls having heard complains inside Sweden that their athletes should have access to the same arsenal of methods as their foreign competitors:
I certainly think that some people had the interpretation that the method was unethical but unfortunately allowed because it wasn’t banned – mostly to give the Swede the same preconditions that the athletes from the other countries had. I can certainly hear the same interpretation yet today about many things – high altitude housing, pressure dressing during exercise etc.
The researchers of the GIH also inquired Swedish blood banks whether they had offered their services for athletes and every blood bank answered in negative except Karolinska Institutet, the institution that had assisted the GIH researchers in the research process. Based on this information, there was no reason for Ekblom to believe that that blood doping was in widespread use in Sweden.*
*Dr. Hans Howald also reported from a 1977 conference where doping methods were discussed that ”[a]ccording to the information received by Dr. Ekblom, blood transfusions have not yet been carried out, at least in Scandinavia, on top level athletes for the purpose of improving performance during important competitions (this is true above all as regards Lasse Viren and Anders GaÅNrderud)”. (Howald, 1978)
Gossip is always gossip, but perhaps more damning accusation has labeled directly again Ekblom by 1964 Olympic gold medalist speed skater Jonny Nilsson, who has claimed on a few occasions that the physiologist asked him to become a subject of the blood reinfusion tests in early 1966, only shortly before the FIS Nordic World Ski Championships in February. The offer that Nilsson refused took place during a training camp at Davos, Switzerland. (Wikström, 1999)*
*Finnish historian Erkki Vettenniemi claims in his book about Finnish skiing doping history that Jonny Nilsson told publicly about the blood doping ”offer” almost right after the blood doping research was revealed in 1971. (Vettenniemi, 2017a)
Ekblom – who had become a coach of the Swedish Speed Skating Union in 1964 and researched the physiology of that sport extensively – recalls having been at the Davos camp and that many blood samples were indeed drawn as the effect of altitude was researched and he also later has recalled having discussed about ongoing blood reinfusion research with Nilsson during the late 1960s. ”I know that I brought a bicycle ergometer with me to Davos and we did lactic acid test”, he recalled the training camp over thirty years after the incident. ”Perhaps we did blood volume tests to Jonny Nilsson”.
Even when their recollections about what happened in the late 1960s diverge, Nilsson has wanted to emphasize that it was it wasn’t doping but a research project, nothing else. ”Björn is not a wrongdoer”, he wanted specifically emphasize regarding the Davos-incident in 1999.
Ekblom reveals that he has discussed the subject matter with Nilsson and they have no disagreement anymore about what happened. There was a misunderstanding which could’ve been because it is true that they did discuss the ongoing blood doping research regularly during the late 1960s when Ekblom spent time with the speed skaters. While Ekblom has emphasized in media that blood doping ”didn’t even exist in 1966”, it is possible that they did discuss about the item already in January-February 1966 as a research topic, because if Ekblom and Åstrand presented their first results in August 1966, the idea of blood doping research must’ve started to materialize around the time when Nilsson recalls the ”offer” being made.*
*Ekblom traces back his reluctance to participate in doping being heavily influenced by his experiment in a one-night orienteering race when he had a magnificent race almost until the end, but he took an illegal choice of route and should’ve been disqualified. ”Nobody asked about the thing, but cheating it certainly was”, Ekblom recalls the incident today. ”I felt so ashamed about the second place in the competition that I decided never to cheat again”. Not only being an eminent physiologist, Ekblom was also an accomplished orienteerer and the Swedish champion of night-orienteering in 1964.
The peripheral counterattack
Whereas the research trends and results of the 1960s stressed the importance of the ”central” factors in limiting maximal oxygen uptake, there was another line of research that started to gain momentum around the time when the blood doping research started.
“Until quite recently it was generally believed that the improvement in exercise capacity that occurs in response to regularly performed endurance exercise is due to increased delivery of blood and oxygen to the working muscle cells made possible by exercise-induced cardiovascular adaptation. Endurance training was equated with training the ‘oxygen transporting system’”, wrote one John O. Holloszy in 1973, only a year after the first blood doping study was published. ”However, within the past six years, evidence has accumulated which shows that, in addition to the cardiovascular adaptations, major adaptations also occur in the skeletal muscles which result in an increase in the capacity for aerobic metabolism”. (Holloszy, 1973)
John Holloszy was an eminent physiologist and very modestly leaves out that the ”accumulation” started in 1967 when his outstanding research paper was published by the Journal of Biological Chemistry shows that there was enormous adaptability at the muscle level associated with endurance exercise, of which the most eminent was a huge increase the in the mitochondrial content of the trained muscle. (Holloszy, 1967) Mitochondria are the sites that ”consume” the oxygen, so theoretically doubling the amount could double the oxygen consumption capacity of muscles at least at the peripheral level. While at first look this doesn’t look such a big deal, the implications were clear. If the vulgar and simplistic version of the central limitation theory went that Vo2Max was related only to the amount of oxygen delivered by heart, why was there any kind of adaptation at the peripheral level at all?
While the possibility of peripheral limitation was seriously considered as the key limiting factor in the oxygen delivery chain quite early on, the muscle itself had been very understudied area before the late 1960s at least from the endurance type of activity viewpoint. Now the research wasn’t just a few random studies, but there emerged an enormous body of literature, of which most was apparently in contradiction with the ”central” theories focusing on oxygen delivery as the key limiting factor. Even some blood reinfusion researchers considered this as a possibility when the reinfusion just didn’t seem to increase performance and when Melvin H. Williams and his coauthors speculate about why their experiment failed, they have one 1972 lecture by Holloszy in their references. (Williams et al, 1973)
”Within some few years in the early 1970s, a wealth of data appeared in the literature, all pointing at the enormous adaptability of the skeletal muscle in response to aerobic training”, could Bengt Saltin and his coauthor Sören Strange write later about this line of research, pointing to research on elevated mitochondrial and capillaries levels in the aerobically trained muscles that was conducted during this time period. ”Without a doubt, the oxygen extracting and utilizing the capacity of skeletal muscle came into focus in the mid-1970s as the key to the understanding of what caused maximal oxygen uptake to vary between individuals and with physical activity level”. (Saltin & Strange, 1992)
To add validity to the importance of the peripheral factors as a possible key limitation of Vo2Max, Lennart Kaijser from the Department of Clinical Physiology of the Karolinska Institutet took an attempt to modify the amount of oxygen delivered to the muscles and conducting various types of performance tests on his subjects for his doctoral thesis published in 1970. Unlike some researchers who had used different mixtures of oxygen and air, Kaijser used high air pressure generated in a hyperbaric chamber, where oxygen availability to the muscles should’ve been higher.
Whereas breathing of oxygen ”enriched” air had increased Vo2Max pretty consistently in research papers since the 1920s, this didn’t take place this time with higher air pressure and unlike expected, the data didn’t support the theory that the muscles could use the extra oxygen offered.
Even when the subject of ”enriched air” had given consistent results in the past, many blood doping skeptics and proponents of the peripheral theories would cite Kaijser’s conclusion that the capacity of the cardiovascular system was limited to the capability of muscles to use the ”offered” oxygen. One Finnish hematologist influenced by Kaijser’s research also draws blood doping-related implications from this material when lecturing about the blood doping literature in 1976. ”It is pointless to try to enhance the oxygen delivery through transfusion, because it doesn’t cause a change in the oxygen utilization by the muscle. The amount of oxygen offered could be increased, but the muscle isn’t capable to utilize more oxygen than that it has adapted to use through an earlier exercise regimen”. (Remes, 1976)
Whereas Kaijser’s work dealt with acute manipulation of the system, of Ekblom’s closest colleagues particularly Bengt Saltin was very interested in what types of changes endurance training caused in muscle and in the mid-1970s he coauthored the famous experiment when the scientists tested how weeks of endurance training using only one leg cycling affected Vo2Max figure of both the trained and the untrained leg.
The maximal oxygen uptake increased by 23 % when work was performed only by using the trained leg, but only 7 % in the non-trained leg. The question then was the obvious one. If the ”central” factors were most important for oxygen uptake, why didn’t the Vo2Max figure of both legs improve in tandem? (Saltin et al, 1976) ”The present results suggest that the local adaptation of skeletal muscle to training is of primary importance for enhancing work capacity and oxygen uptake”, Saltin summed up the paper shortly later. (Saltin, 1977)*
*Saltin and his coauthors also wrote in the paper that the findings ”focuses attention on peripheral factors as being at least as essential for the cardiovascular performance during exercise as any central factors”, adding that German researcher named Muller came to the similar conclusion ”already in 1942”. Saltin would later write many chapters on books and papers on the history of thought of exercise physiology.
While this research raised questions about the importance of cardiovascular system as a determinant of Vo2Max, it wasn’t in contradiction with the ”central theory”, because the limiting factor of oxygen uptake could’ve been different with different types of work, a point emphasized by Ekblom some a quarter of a century after Bengt Saltin and his coauthors had published their interesting paper. ”Whether or not `peripheral’ factors such as capillary density, enzyme concentrations, and muscle mass limit oxygen consumption during heavy exercise has been a matter of controversy for many years”, Ekblom wrote in 2000 in a review on what was known then about blood doping. ”However, it depends on the type of exercise carried out. During exercise using small muscle groups such as during isolated dynamic arm work these `peripheral’ factors are of the utmost importance for, and do limit, the aerobic energy turn-over and endurance”. (Ekblom, 2000)
Ekblom’s view today is that there could be a difference in different types of sports such as cycling vs. running, where, in cycling the peripheral factors and muscle level adaptation can play a relatively more important role. “It deals with the question of P50 and mitochondrial capacity and function”, Ekblom said of what he sees as the most pertinent peripheral issues today. ”Everything is not clear”.
The question was of importance to him even in the 1970s when he tested how various combinations of limbs affected Vo2Max and there was even discussion in the decade about a paper on how blood doping affected the performance of isolated limbs, but as time was a scarce resource, the study never materialized. But one test was conducted using only arm work after reinfusion. While there was no increase in Vo2Max, time to exhaustion did increase.
One muscle-related finding was also that when it was known that there were different types of muscle fibers (fast vs. slow), the muscle theories as a key limiting factor of Vo2Max gained some extra momentum when it was also noticed that there was a correlation between the amount of endurance type ”slow” type I muscle fibers and maximal oxygen uptake. (Bergh et al, 1978)
Ekblom’s blood doping research is barely mentioned in this research on the peripheral limitation theories, but his other research was of great interest to the scientists interested in the muscle adaptation to aerobic exercise. It didn’t go unnoticed that Ekblom himself had observed that Vo2Max barely fell even after cardiac output had been reduced by some 12 % in the 1972 beta-blockade experiment when maximal heart rate was reduced by some 30-40 beats. Holloszy also found it most relevant that in many longitudinal training studies the increased stroke volume of heart accounted only roughly half of the increased Vo2Max whereas the other half was that muscles could use more of the oxygen of every given unit of blood leaving left ventricle. (Holloszy 1973) Holloszy concluded that oxygen consumption wasn’t only about oxygen delivery but that other factors were equally important.
One of the materials referenced by Holloszy was Björn Ekblom’s thesis published in 1968 under the title Effect of physical training on the oxygen transport system in man. (Ekblom, 1968)
If it wasn’t clear what to make about this material in the 1970s and how to contrast it with the emerging blood reinfusion research, the muscle itself became a real research topic from endurance viewpoint and there evidently happened a lot at the peripheral level.
This is part three of a multi-part series titled “Limiting Factors – A Genesis of Blood Doping”.
The full bibliography for this research can be found at the end of Limiting Factors – A Genesis of Blood Doping (part one).