VIAGRA: THE LATEST RESEARCH ON EXERCISE PERFORMANCE

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Written by Thomas Fahey

Viagra has moved from the bedroom to the locker room. The buzz on the street was that Yankee superstar Roger Clemens had a bottle of Viagra disguised as vitamin pills stashed in his locker. Last May, Italian cyclist Andrea Moletta was removed from the Giro d'Italia after police found a cache of Viagra and syringes in his car. Not surprisingly, the tabloids had a field day following these incidents and charged that legions of athletes in baseball, football, bodybuilding and Olympic sports took Viagra to boost endurance and physical performance. The World Anti-Doping Association (WADA) considered banning Viagra before the Beijing Olympics, but backed off because it had no evidence that the drug provided a competitive advantage.

What do firm erections have to do with sports like bodybuilding? Viagra improves blood flow control. Muscles need plenty of blood to remove wastes and deliver energy, oxygen, and hormones. Increased blood flow could speed the delivery of key amino acids to the muscles, which would promote muscle protein synthesis and growth. It seems reasonable that Viagra could boost performance and that bodybuilders might take it.

A Stanford University study by Ann Friedlander and colleagues published in 2006 triggered the Viagra craze among athletes. The researchers found that Viagra improved cardiovascular capacity during exercise on a stationary bike at a simulated altitude of 12,710 feet but not at sea level. Viagra increased cardiac output (blood pumped by the heart per minute), stroke volume (blood pumped by the heart per heartbeat), and oxygen saturation (percent of red blood cells carrying oxygen). Cycling performance at altitude improved by 15 percent. The drug increased exercise capacity by reducing blood pressure in the lungs, which increases at high altitude. Not all subjects benefited from the drug— there were responders and non-responders. Other researchers confirmed the Stanford results and also showed that Viagra improved exercise capacity in people suffering from lung disease and heart failure.

Bodybuilding is an incredibly difficult sport that requires years of backbreaking work to achieve success. Most athletes will do whatever it takes to increase muscle mass and win contests. It’s understandable that they take Viagra: it’s not on any banned substances list; it’s readily available; it has few side effects; and it might provide a significant edge. The fact that it only worked in some people above 12,000 feet altitude and didn’t work at sea level was somehow lost in the shuffle.

Why Viagra Might Be an Effective Bodybuilding Drug

 Viagra (sildenafil) is one of three FDA-approved, erection-promoting drugs called PDE-5 inhibitors that also include tadalafil (Cialis) and vardenafil (Levitra). They work by inhibiting the PDE-5 enzyme, which then increases the concentration of a chemical called nitric oxide that promotes blood flow to the penis and other tissues throughout the body. Blood vessels, smooth muscle, skeletal muscle, blood platelets, and lung tissue contain this and similar PDE enzymes. In addition to promoting erections, PDE-5 inhibitors decrease systemic blood pressure, lung blood pressure, lung resistance, and promote coronary (heart) blood flow. Long-term use improves endothelial function, which is critical to blood flow control.

 The drugs reduce stress in pressure-overloaded hearts, which is important for bodybuilders because large increases in muscle tension restrict blood flow to working muscles. Increasing muscle blood flow during training could increase muscle strength, size, and fitness, while reducing stress on the heart. They also improve lung blood flow and boost quality of life in patients suffering from lung disease.  These drugs have promising pulmonary and cardiovascular applications that go beyond firm erections.

To date, no study has found that Viagra improves exercise performance in athletes at sea level. The drug is helpful in people with blood pressure limitations that interfere with oxygen transport to the tissues. For example, lung blood pressure increases substantially in some people at altitude, which makes it difficult to move oxygen from the air into the bloodstream. Viagra reduces lung blood pressure, which enhances oxygen consumption and the capacity to exercise.

A small percentage of elite endurance athletes have a performance imbalance between the heart and lungs. Their powerful hearts exceed breathing capacity, which causes a mismatch between the pulmonary and cardiovascular systems. Viagra might increase lung function to match their superior heart capacity, which could give them a significant competitive advantage. However, other athletes might benefit as well.

Physical inactivity, diets high in saturated and trans-fats and simple sugars, and reduced muscle mass impair the ability of insulin receptors to regulate carbohydrates, amino acids (building blocks of proteins) and fats. Insulin sensitivity affects the health of the endothelium, the cells that line the blood vessels. These cells release nitric oxide (NO) that opens blood vessels in tissues throughout the body. Long-term use of Viagra has training-like effects on the endothelium, which increases its capacity to release NO. While the Viagra-induced improvements in blood flow control might be greater in men suffering from poor metabolic health, they might also promote blood flow in the muscles and nervous systems in bodybuilders and physically fit adults. Viagra doesn’t appear to increase endurance performance following short-term use, but it might have long-term benefits in well-trained athletes.

Long-term use of Viagra might also benefit metabolic capacity by enhancing blood sugar control and increasing testosterone levels. Scientists from Vanderbilt University School of Medicine found that the drug helped restore energy balance and boosted insulin metabolism in mice fed high-fat diets (compared to a placebo). The animals showed lower blood sugar and insulin levels and improved blood sugar regulation after a high-carbohydrate meal. They also lost bodyweight and fat mass during the 12-week study. In humans, long-term use of Viagra increased the production of the blood vessel controlling chemical nitric oxide, which has strong links to insulin metabolism.

 Viagra boosts testosterone, which is a critical hormone for increasing muscle mass, strength, and aggressiveness— all critical for athletes. Testosterone is linked to sexual arousal and performance. Middle-aged men who take testosterone supplements improve sex drive, capacity for erections, self-confidence, and aggressiveness. Italian researchers found that total and free testosterone levels increased by 50 percent in men treated for erectile dysfunction with Cialis or Viagra. It’s not clear whether these drugs increased testosterone directly or if they increased it indirectly through increased sexual activity. Frequency of sexual intercourse was greatest in men who took Cialis (a longer-acting PDE-5 inhibitor), which makes it the preferred drug for men in stable relationships. Men who had the most sex also had the highest testosterone levels.

Factors affecting testosterone include psychological health, diet, exercise, and sexual activity. Men who have a lot of sex are happier, more confident, and have better-functioning sex organs than men who don’t. The sex organs— like your muscles— function best when you use them, so Viagra might give them a boost. We don’t know if Viagra increases testosterone levels in healthy, fit bodybuilders.

Long-term use of Viagra might also increase muscle strength, power, and size by triggering biochemical pathways that increase protein synthesis and prevent protein breakdown in muscle cells. As discussed, Viagra increases nitric oxide (NO) release by the blood vessels. NO helps turn on protein synthesis in muscles, particularly when the fibers are under tension or stretch. NO also triggers the formation of satellite cells that add mass to the muscle fibers. To date, no study has shown that Viagra and similar drugs have steroid-like effects in athletes, but we can infer from biochemical studies that they might.

 Viagra is on WADA’s Radar

WADA first took notice of Viagra following the Stanford University study and reports that the drug was given to greyhounds to improve running performance. They were concerned that Viagra might improve performance at lower altitudes and provide a competitive advantage at venues such as Denver, Mexico City, or areas hosting the Winter Olympics. The margin of victory is often a matter of seconds in endurance events in cycling and cross-country skiing, so a drug that provides even a small advantage could be very significant.

WADA is currently funding a series of studies at Marywood University in Scranton, Pennsylvania and at the University of Miami, to determine the effects of Viagra on exercise capacity and performance at sea level, moderate altitudes, and in polluted environments. They also want to know if the drug has different effects in men and women. The results of these studies will determine whether Viagra ends up on the banned substances list.

 Will Viagra Make You a Superstar?

 Viagra can help make you a sexual Olympian, provided that you have game, good hygiene, and a reasonably firm body. It definitely won’t get you a spot on the Yankee’s roster or the Olympic team if you don’t have the talent. To date, no study has found that Viagra improves exercise capacity at sea level. However, long-term use of the drug might promote muscle protein synthesis and improve metabolic fitness enough to have a small effect on endurance or strength. Viagra and similar drugs have side effects; so don’t use them without following the advice of a physician. We need many more studies before we can adequately assess the effects of these drugs on exercise capacity and athletic performance.

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