The science (and scandal) of doping in cycling


I began commuting by bicycle about two years ago and I am now hooked on cycling. For about 18 months I rode around on my hip(ster) single-speed, Charge Plug (mine is dark blue). But, I began to steadily increase the distances I was riding on weekends and having one gear became limiting, particularly for going up hills. So after my mate Paul got a road bike I decided I should too. It took about two rides to get used to the bike and within a couple of months I was riding at least eight hours a week, including a long three/four hour ride (100km) on Saturday or Sunday. I am obsessed with cycling now and can't get enough of it. So much so that for the first time since I was about 10 or 11 I watch sport intently.

Because of my obsession with cycling it often comes up in conversation with people. In these conversations, doping is often brought up by the other party, and usually quite early on in the piece. Obviously I can understand why this occurs: cycling has a long history of doping scandals. In recent history there have been some particularly prominent incidences including the Festina AffairOperaciĆ³n Puerto and of course the latest Lance Pharmstrong saga with the 1000 page reasoned decision from the United States Anti Doping Agency (USADA)

So the obvious question that arises is why is cycling so bad for doping? There are several potential reasons but first I think it is worth going into some of the specifics of what doping is in a general sense, understanding it in a basic biochemistry framework and how this relates to cycling. I will attempt to keep the discussion grounded in science and relatively simple but may stray into subjective opinion from time to time.

 So what is doping? Most people have a general understanding that doping makes athletes better at sport. But it is important to understand how doping does this. It is in understanding what or how doping works that will point to one of the reasons that doping has been so pervasive in cycling. Doping in endurance sports is typically related to improving aerobic capacity allowing athletes to go faster for longer. The pathway through which this is achieved is by using 'something' to elevate haemoglobin or red blood cell levels (haematocrit levels): haemoglobin is the component of blood that carries oxygen so by having more haemoglobin the oxygen carrying capacity of blood is increased. Typically males have a haematocrit level of around 45 percent and females around 40 percent. So quite simply, the most common form of doping in cycling (and other endurance sports) is to increase the proportion of red blood cells in your blood.
So how does more oxygen help you go faster for longer? I mentioned aerobic capacity previously but it is useful to look at what this means. Our bodies need energy to do all metabolic tasks and to power the muscles. I used the two images in a lecture on cellular respiration for my foundation biology class this semester to illustrate that both Philippe Gilbert winning the world champs and sleeping polar bears need energy, but that some activities require more energy than others. Energy in mammals is stored in the form of a polysaccharide called glycogen (glycogen is basically a long chain of glucose-sugar-molecules). The body then uses a process, cellular respiration, to 'release' usable energy in the form of the molecule ATP: ATP is often referred to as the 'currency of energy' and is the molecule that powers metabolic processes in cells and the biochemical energy to power muscles.
BMC racing team
The final stage of cellular respiration is called oxidative phosphorylation and it is this process oxygen plays a crucial role. The process is relatively complex and so won't go into too much detail. What is important to know is that oxidative phosphorylation produces the ATP energy molecules with the help of oxygen. During intensive exercise the demand for ATP can outstrip the supply if there is not enough oxygen available for the ATP-producing reactions. It is at this stage when demand outstrips supply that you feel the burn in your muscles. This is commonly thought to be because of lactic acid build-up. This, however, is not the case. Larry Moran has an excellent post that debunks the idea of acidosis (the burn). Nonetheless, regardless of what the specifics of the burn are we know it is the result of energy use exceeding energy production in which oxygen is a key ingredient.     

Knowing the basics of how cellular respiration works and how doping increasing the oxygen carrying capacity of the blood allows us to see the benefits for cycling over some other sports. Most competitive sports require a high level of fitness, but for many sports there is a an additional set of skills required. Consider rugby or football for example. Both require a high level of fitness but ball handling skills etc. are also extremely important. Compared to cycling the period of time over which intense activity needs to be maintained in rugby and football is relatively low. Rugby and football games last 80 and 90 minutes respectively. Professional road cycling races on the other hand are significantly longer. One-day races may last four hours for a short race to and over six for long ones. Then there are the multi-day stage races - the most famous is of course the Tour de France which lasts three weeks with the riders averaging over 180km per day in next year’s edition (excluding the two rest days and three time-trials). When you look at the differences in activity periods it makes sense that over such long distances even small differences in fitness/aerobic capacity makes a huge difference in cycling. So it makes sense that doping is 'useful' in cycling because it can result in significant gains in aerobic fitness. And compared to many other non-endurance sports aerobic fitness is the single most important factor contributing to success in cycling. Therefore, if there were a way to increase aerobic fitness quickly you can see how it might be tempting for some.  (At this stage it is important to note that doping can be used either in or outside of competition. In competition the benefits are obvious. Outside of competition doping can allow you to train more and harder which is beneficial for muscle conditioning, blood vessel development and increasing mitochondria levels in cells. Mitochondria are the power stations of the cell in which cellular respiration takes place. The more mitochondria you have the more efficiently you can produce usable energy (ATP).)

How do you boost haematocrit levels? There are two way to do this. One is using a substance to stimulate red blood-cell production, and the other is blood doping. The most commonly used substance by cyclists to boost haematocrit is erythropoietin (EPO). EPO is a hormone that occurs naturally in humans (and other animals) that regulates red blood cell production. However, EPO is now synthesised as a drug to treat patients suffering from anaemia - a disease related to low red blood cell levels.  It is this synthesised EPO that sports people use to do the cheating. Until recently (2001) there was no test for EPO and even today it can be difficult to detect if taken 'correctly'. Thus, combining the potential gain from EPO and difficulty in detecting it why the hell not use it? Of course you could say that is was ethically or morally wrong, a point with which I agree. But, as some have argued, if other people are doing it and they are winning, I am not going to win if I don't do it too. Anyways I have strayed into subjective territory which I wanted to avoid. 

With the advent of the EPO test riders began to seek alternatives. Blood doping became the cheating of choice. Blood doping is quite straight forward if not a little creepy if you ask me. Riders will have blood extracted and stored. Then, during a stage race after haematocrit levels have dropped (this happens due to the high physiological stress), the blood is re-infused to top-up red blood cell counts. There is no direct test available for blood doping but it is possible to find evidence that indicates that it has taken place using a rider's biological passport. The biological passport is essentially a way comparing a rider’s normal blood to their blood taken during random testing controls. If there are significant variations from normal it suggests doping.

Now that we know how doping works and how it benefits cycling we can understand begin to reason why is so prevalent in the sport.  But, is it really more prevalent than other sports? Another sport where doping is known to be common is cross-country skiing. Cross-country skiing is an extremely demanding endurance sport and so it makes sense that doping can result in significant gains. However, we hear very little about it because compared to cycling it has relatively small coverage outside of the countries that participate in the sport. For me one of the most important things is testing. This again  relates back to the potential gains  available from doping in cycling. Cycling has one of the (the) most rigorous testing regimes in any sport. After every race, or stage in a stage race, you see riders going into little booths to give doping control samples. But, in addition to in-competition testing cycling also has rigorous, bordering on invasive, out-of-competition testing. Basically testers can show up at your door any time and test you. Furthermore, if you aren't at home you need to be able to account for exactly where you were and what you were doing. I know of no other sport that does this. I read a quote from a pro cyclist who claimed he gets tested more in a year than a professional footballer does in their whole career. Whether that is entirely true or not it still demonstrates the point. Thus, it seems more difficult to get away with doping in cycling than other sports*. That means dopers get caught more often than they might be in other sports.

*Of course the Pharmstrong saga suggests otherwise but there is much more to that situation than passing tests and should be viewed in a somewhat different light.