The previous video examined performance enhancing drugs designed to improve strength and muscle mass. This video will examine performance enhancing drugs designed to improve performance in activities that have a large aerobic or endurance component. This will include events ranging from a 5K race, to participation in the Tour de France. I will begin the technique of blood doping. The concept whereby blood doping will lead to an increase in performance relates to oxygen delivery. If the sport or event requires exercising close to VO2max, where the rate of oxygen delivery and utilization could potentially be a limiting factor, then artificially increasing one's oxygen carrying capacity may improve performance. Blood doping has been shown to be very effective in improving race times and performance. In years past, before detection of doping became more sophisticated, several Olympic gold medalists in the 5 and 10K races employed this technique. Just as disturbing, during the seven period between 1999 and 2005, when Lance Armstrong won every Tour de France, 87% of the top ten finishers, that's 61 out of 70 cyclers, were confirmed dopers or suspected of doping. Blood doping is accomplished by increasing the number of red blood cells in the circulation. This will also lead to an increase in total blood volume. As 98.5% of the oxygen transported in the blood is bound to hemoglobin, located within the red blood cells, increasing their numbers will greatly enhance the oxygen carrying capacity of blood. In well trained endurance athletes, who have an abundance of mitochondria and skeletal muscle, and thus the ability to utilize the extra oxygen being delivered, this can lead to a significant increase in maximal oxygen consumption and improved performance. The three most common ways athletes attempt to increase their red blood cell mass are listed here. A classic technique for blood doping is the reinfusion of the athlete's own red blood cells. Some athletes relocate to high altitude, as a well established adaptation of chronic hypoxic exposure is an increase in red blood cell numbers. Recently, athletes have discovered a shortcut that is less involved than the classic blood doping method. This involves the injection of erythropoietin, a hormone produced by the kidneys that stimulates red blood cell production in bone marrow. A classic red blood cell reinfusion method involves the withdrawal of two to four units, or 900 to 1800 millilitres of the athlete's own blood. After the blood is spun down, the plasma is immediately reinfused into the athlete to help maintain blood volume, while the now packed red blood cells are preserved and frozen for later reinfusion. Over the next four to six weeks, the athlete will naturally replace the red blood cells lost, returning to pre-withdrawal levels. A day or two before a big competition, the packed red blood cells are reinfused and the athlete's red blood cell concentration immediately increases, dependant upon the amount infused. As such, the oxygen carrying capacity of the athlete's blood has been significantly enhanced. The increase in blood volume alone from the reinfusion can increase maximum cardiac output, and thus VO2max, as previously discussed in the equation. The larger blood volume results in a greater venous return to the heart, and subsequently, a larger maximal stroke volume, thereby increasing cardiac output. Here are the results from just one study demonstrating the typical responses to this classical blood doping technique. 24 hours after reinfusion of 750 millilitres of packed red blood cells, subject's hemoglobin content increased on average 27%. More importantly, this translated into a significant improvement in performance as measured by VO2max, and runtime to exhaustion, compared to when the same subjects were tested pre-infusion. More recently, in order to avoid the cumbersome classic blood doping technique, which can also affect your ability to train during the initial weeks after donating blood, athletes have taken to injections of erythropoietin, or EPO. As already stated, EPO is a hormone produced by the kidneys that stimulates red blood cell production in bone marrow. The majority of studies suggest that EPO injections are effective in increasing red blood cell numbers, VO2max, and performance time in elite athletes. However, unlike the classic blood doping technique which is relatively safe, when reinfusing one's own blood, EPO injections are not without significant risks. Not everyone responds the same way to EPO administration, and thus care must be taken to avoid making the blood too thick or viscous. This will greatly increase the risk for blood clots and pulmonary emboli. When EPO first appeared in sports in the late 1980s and early 1990s, it was responsible for over 20 deaths of European cyclists. Presently, greater precautions when administering EPO have dramatically reduced the mortality rate. Next, let's examine how caffeine can potentially serve as a performance enhancing substance. Caffeine directly stimulates the central nervous system, mimicking the actions of the sympathetic nervous system. As it relates to athletic performance, the proposed effects of caffeine include increased mental alertness, increased mobilization and utilization of fats, and the delayed onset of fatigue. Here is one study demonstrating caffeine's effect on fat mobilization and utilization. Competitive cyclists consumed either a caffeinated or decaffeinated beverage one hour prior to exercising at 80% of VO2max. The elevated glycerol and free fatty acid levels in the blood, along with a lower respiratory exchange ratio, indicate that during the caffeinated trial, the cyclists were able to mobilize and utilize fats to a greater extent when compared to their decaffeinated trial. This greater use of fats would delay both muscle and liver carbohydrate depletion. Notice that these athletes were able to exercise approximately 20% longer during the caffeinated trial at the same exercise intensity compared to the decaffeinated trial. This figure demonstrates that more caffeine is not necessarily better, as no dose response relationship was observed for improvement in endurance performance above the lower dose of five milligrams of caffeine per kilogram of body weight. However, I will point out that these cyclists were not regular coffee drinkers. It is possible that habitual users may develop a tolerance to caffeine, whereby a higher dose may be required to have the beneficial effects on performance. Interestingly, caffeine can potentially have a performance enhancing effect on short term, high intensity exercise, such as sprinting. This figure shows the split times for elite swimmers, with or without prior ingestion of caffeine. Split times were significantly faster at all distances tested during the caffeinated trial. While the mechanisms responsible for this ergogenic effect of caffeine remain elusive, caffeine is known to directly act on muscle, possibly altering calcium flux from the sarcoplasmic reticulum. The final performance enhancing technique that I will discuss is known as buffer loading. As discussed in the video on fatigue, short term, high intensity exercise can produce severe metabolic acidosis in muscle leading to fatigue. The high concentration of hydrogen ions can interfere with calcium's role in cross-bridge formation and, thus, tension development in muscle. The athletes who engage in these types of activities could potentially benefit from artificially boosting their acid buffering capacity prior to exercise. Shown here is one of many studies indicating that buffer loading may extend time to fatigue and power output during intense activities. In this study, when trained women were given sodium bicarbonate prior to one bout maximal of exercise, they were capable of performing at a higher peak power and intensity per 60 seconds when compared to when they performed the exact same test with a placebo or no supplement at all. Thus, if metabolic acidosis is a factor contributing to fatigue, buffer loading may delay the onset of fatigue and enhance performance. In summary, blood reinfusion and erythropoietin injections will increase red cell mass and possibly enhance performance in certain activities. Caffeine can be effective in improving endurance times and muscle force. Buffer loading may delay the onset of fatigue during short term, high intensity exercise. This concludes module three. In the fourth and final module, I will discuss the very important role that exercise plays in health and disease. This will include the prevention and treatment for obesity, heart disease, diabetes, cancer, and aging. I hope to see you there.
