Tuesday, August 30, 2016

We Are Nowhere Close to the Limits of Athletic Performance

[ed. See also: Born to Rest.]

For many years I lived in Eugene, Oregon, also known as “track-town USA” for its long tradition in track and field. Each summer high-profile meets like the United States National Championships or Olympic Trials would bring world-class competitors to the University of Oregon’s Hayward Field. It was exciting to bump into great athletes at the local cafe or ice cream shop, or even find myself lifting weights or running on a track next to them. One morning I was shocked to be passed as if standing still by a woman running 400-meter repeats. Her training pace was as fast as I could run a flat out sprint over a much shorter distance.

The simple fact was that she was an extreme outlier, and I wasn’t. Athletic performance follows a normal distribution, like many other quantities in nature. That means that the number of people capable of exceptional performance falls off exponentially as performance levels increase. While an 11-second 100-meter can win a high school student the league or district championship, a good state champion runs sub-11, and among 100 state champions only a few have any hope of running near 10 seconds.

Keep going along this curve, and you get to the freaks among freaks—competitors who shatter records and push limits beyond imagination. When Carl Lewis dominated sprinting in the late 1980s, sub-10 second 100m times were rare, and anything in the 10-second flat range guaranteed a high finish, even at the Olympics. Lewis was a graceful 6 feet 2 inches, considered tall for a sprinter. Heights much greater than his were supposed to be a disadvantage for a sprinter, forcing a slower cadence and reduced speeds—at least that was the conventional wisdom.

So no one anticipated the coming of a Usain Bolt. At a muscular 6 feet 5 inches, and finishing almost half a second faster than the best of the previous generation, he seemed to come from another species entirely. His stride length can reach a remarkable 9.3 feet,1 and, in the words of a 2013 study in the European Journal of Physics, demonstrated performance that “is of physical interest since he can achieve, until now, accelerations and speeds that no other runner can.”

Bolt’s times weren’t just faster than anyone else in the world. They were considerably faster even than those of a world-class runner from the previous generation that was using performance-enhancing drugs. The Jamaican-born Canadian sprinter Ben Johnson achieved a world-record time of 9.79 seconds at the 1988 Olympic Games, beating Lewis and boasting that he’d have been faster if he hadn’t raised his hand in victory just ahead of the finish line. It would later be found out that he’d been using steroids.

Even the combination of an elite runner and anabolic steroids, though, was not enough to outcompete a genetic outlier. Bolt achieved a time of 9.58 seconds at the 2009 World Athletics Championship, setting a world record and beating his own previous record by a full tenth of a second.

We find a similar story in the NBA with Shaquille O’Neal. O’Neal was the first 7-footer in the league who retained the power and agility of a much smaller man. Neither a beanpole nor a plodding hulk, he would have been an athletic 200-pounder if scaled down to 6 feet in height. When Shaq got the ball near the hoop, no man (or sometimes even two men) could stop him from dunking it. Soon after his entry into the league, basket frames had to be reinforced to prevent being destroyed by his dunks. After the Lakers won three championships in a row, the NBA was forced to change their rules drastically—allowing zone defenses—in order to reduce Shaq’s domination of the game. Here was a genetic outlier whose performance was unequalled by anyone else in a league that has long been criticized for its soft anti-doping policy; for example, it only added blood testing for human growth hormone to its program last year. Whatever doping may have been going on, it wasn’t enough to get anyone to Shaq’s level.

By comparison, the potential improvements achievable by doping effort are relatively modest. In weightlifting, for example, Mike Israetel, a professor of exercise science at Temple University, has estimated that doping increases weightlifting scores by about 5 to 10 percent. Compare that to the progression in world record bench press weights: 361 pounds in 1898, 363 pounds in 1916, 500 pounds in 1953, 600 pounds in 1967, 667 pounds in 1984, and 730 pounds in 2015. Doping is enough to win any given competition, but it does not stand up against the long-term trend of improving performance that is driven, in part, by genetic outliers. As the population base of weightlifting competitors has increased, outliers further and further out on the tail of the distribution have appeared, driving up world records.

Similarly, Lance Armstrong’s drug-fuelled victory of the 1999 Tour de France gave him a margin of victory over second-place finisher Alex Zulle of 7 minutes, 37 seconds, or about 0.1 percent. That pales in comparison to the dramatic secular increase in speeds the Tour has seen over the past half century: Eddy Merckx won the 1971 tour, which was about the same distance as the 1999 tour, in a time 5 percent worse than Zulle’s. Certainly, some of this improvement is due to training methods and better equipment. But much of it is simply due to the sport’s ability to find competitors of ever more exceptional natural ability, further and further out along the tail of what’s possible.

We’re just scratching the surface of what genetic outliers can do. The normal distribution we see in athletic capabilities is a telltale signature of many small additive effects that are all independent from each other. Ultimately, these additive effects come from gene variants, or alleles, with small positive and negative consequences on traits such as height, muscularity, and coordination. It is now understood, for example, that great height is due to the combination of an unusually large number of positive variants, and possibly some very rare mutations that have a large effect on their own.

The genomics researcher George Church maintains a list of some of these single mutations. They include a variant of LRP5 that leads to extra-strong bones, a variant of MSTN that produces extra lean muscle, and a variant of SCN9A that is associated with pain insensitivity.

Church has also been involved in one of the greatest scientific breakthroughs of recent decades: the development of a highly efficient gene editing tool called CRISPR, which has been approved for clinical trials for medical applications. If CRISPR-related technologies develop as anticipated, designer humans are at most a few decades away. Editing is most easily done soon after conception, when the embryo consists of only a small number of cells, but it is also possible in adults. Clinical trials of CRISPR, when they start this year, will edit existing cells in adults using an injection of a viral vector. It seems likely that CRISPR, or some improved version of it, will be established to be both safe and effective in the near future.

by Stephen Hsu, Nautilus |  Read more:
Image: Cameron Spencer/Getty Images