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How doping works in cycling, explained by a physiologist and former pro rider

We talked to an expert to learn more about how today’s cyclists cheat — from EPO, to salbutamol, to ... uh ... poop doping.

Le Tour de France 2017 - Stage Twenty One Photo by Chris Graythen/Getty Images

Athletes cheat. And one of the best ways to cheat is to take banned substances to give your body a boost.

And there’s no sport and sporting event so inextricably linked to cheating as cycling and the Tour de France. Lance Armstrong is the face of cycling’s doping problem, but in truth the sport was cheating long before Armstrong, and in all sorts of creative ways. That legacy will undoubtedly continue long into the future. Don’t be surprised if you start hearing the term “poop doping” on a regular basis someday.

As for the present, well, you may have heard of Chris Froome, a man approaching Armstrong-ian levels of yellow jersey success who has also become embroiled in a doping scandal. Froome was found with twice the permitted level of salbutamol, an asthma medication, in his system during last year’s Vuelta a España, and was briefly banned from the Tour before being cleared five days before the start of the race.

The point being, cheating in sports is not going away any time soon, nor is it getting any easier to comprehend. To help explain, SB Nation spoke to Dr. Stacy Sims, an environmental exercise physiologist and nutrition scientist at the University of Waikato in New Zealand. Sims was a pro women’s cyclist who later went on to work with men’s pro cycling teams like Saxo and Dimension Data during the Tour de France, advising team chef Hannah Grant on rider nutrition.

Sims understands cyclists’ bodies perhaps as well as anyone can. She answered our questions cycling’s love affair with erythropoietin (better known as EPO), how asthma medication would help a rider — and, yes, if poop doping is really a thing.

EPO is the big thing. What advantage does EPO give you? And how does EPO work?

Dr. Stacy Sims: EPO is the hormone that is released in the kidney when you have a low partial pressure of oxygen. And you can naturally produce it by doing some dehydrated activity in the heat, or you go to altitude, and it’s your body’s drive to need more red cells, because red cells are responsible for picking up and delivering oxygen. So the idea behind taking EPO is to increase that red blood cell production, because with increased red cells, you have increased oxygen carrying capacity, and increased oxygen delivery capacity.

The idea behind lots of people using it is that it is a really fast way for red cell development. But the flip side to that is, if you get too many red cells in your blood and your blood becomes too viscous, then it actually can’t move through the body, which is why they have that cutoff of 50 [percent volume red blood cells to total blood volume].

So your hemoglobin and your hematocrit levels are tightly monitored. We look more at your hematocrit, because it’s your red cell count. And when it starts approaching that 50 mark, and 50 and beyond, that’s a tipping point for someone doping, and it is a health hazard, because if you get too much of that hematocrit, your blood just doesn’t go where it needs to go and it can’t function properly.

Is it possible to get past that 50 mark naturally? Has there ever been anyone who has been able to do that naturally?

SS: It depends on when you test them. If you test someone when they’re dehydrated, like after a max test or something, and they’re sitting around 47 to 48, then you’ll see that they’re 52 because they’ve lost a lot of the water out of their blood, so their blood is concentrated.

There are some anomalies. Cyclists, again, it’s really hard to tease out because of the incidence of doping. I would love to be able to have a clean team and really, as much as people say they are, you have your doubts. But it is possible.

It has an aspect of living in altitude, and having a high testosterone level. Then your body will compensate and produce more red cells just because it needs that for the oxygen, and the testosterone is a drive for producing EPO.

In what ways does doping throw off long-term studies on grand tour riders? And are riders who use EPO likely to have long-term problems?

SS: I think if they use EPO, then they will. Just from the aspect of having a really high hematocrit level, and you have to look at cardiovascular incidences of “sticky cells,” so there’s a higher amount of stuff in the blood — so you have your red cells, and your platelets, and fractions of cells — and if they are under this constant load of exercise and high sugar, then their vessels aren’t as compliant. So longer term, you can have some disorder with regards to vessel compliancy, so they become very stiff, they don’t have as much nitric oxide response, so their blood pressure is off and they’re dealing with high blood pressure.

You can end up with some vascular disease. So the longer term consequence of having that artificially high production of red cells can have a huge impact on overall cardiovascular and total vascular health.

Chris Froome was caught last September with excess Salbutamol in his system. That was new to me. How does excess asthmas medication help a rider?

SS: It is a bronchial dilator. I’ll take it back a step — the whole buzz about beet juice being a vasodilator, increasing blood circulation to the muscles without as much work, it’s the same idea of using clenbuterol or another type of asthma inhaler, where it increases the surface space of the bronchials so you have more oxygen transfer. So effectively with every breath, you can intake and transfer more oxygen to the cells. So again, it’s all about that oxygen delivery.

Is this something that has been common in cycling for a long time? Why don’t we see this happen more?

SS: I think a lot of people use the TUE [Therapeutic Use Exemption] as an excuse. Especially undercards of testosterone or asthma medication, people start to really question the harder drugs of like growth hormone and that kind of stuff. The common medications that are prescribed that can also be ergogenic, if you have a TUE, then it’s almost a carte blanche to use it regardless.

And I think that can be kind of why people are not necessarily bringing it to the table, so to speak. Because there are some people who legitimately need asthma inhalers, and there are some people who have Low T. Low T can be mitigated with energy availability and nutrient timing, and making sure you are on par with your intake, people don’t want to take the time to do it, they’d rather just take the drug.

The same with pseudoephedrine and ephedrine, that was taken off [the permitted substance list] because it was such a powerful stimulant, and such a powerful vasodilator. People can get it over the counter in cold medications, and they’re like, ‘Woah, this is such a significant ergogenic aid, we need to take it off.’ So there are some things that come up.

That’s where this health and performance line comes into play, because you have physicians who are like, ‘We need it for health,’ and then you have people who are monitoring for performance going, ‘Well, actually it enhances performance, are you sure?’ But they can’t necessarily question the physician.

Can I get your opinion on poop doping, and have you been looking into that at all?

SS: Into what doping?

Poop doping. There was a researcher who looked at the gut biomes of professional road racers and compared them to amateur cyclists and found that the best riders had this certain bacteria in their gut, and she posited that you could —

SS: — essentially change your gut microbiome and dope to — yeah.

I mean, in theory it seems like it would work. But in practice, there are so many other factors. We put it kinda also in the epigenetic aspect where you can take in certain things and cause a genetic expression, either over or under expression, and that may or may not enhance performance. This is the same with gut microbiome. I mean, seven days of one type of exposure will completely change a microbiome. So not only do they have to take the probiotics or the actual bacteria that mimics what the pro rider has, they also have to live the lifestyle, they have to be exposed to the same bacteria every day that’s on the counters and the sinks. They have to be exposed to the same food that’s grown in the same soil.

Again, in theory, probably. But in practice, I think it’s much more complex than what she’s talking about.

So you think it’s probably unlikely that someone riding the Tour de France this year is poop doping.

SS: [Laughs] Right.