What explains Usain Bolt's speed? Track fans have been debating that question for years, and now a team of physicists from the National University of Mexico in Mexico City have created a mathematical model that helps explain how the world's fastest man is able to bolt 100 meters in well under 9.6 seconds.
"As far as our study can reveal, he seems to be able to develop more power than other runners," study co-author Dr. Jorge Hernandez, a professor of biophysics at the university, told The Huffington Post in an email. "A way of doing it is that he finds a way to reduce the area (cross section, as we call it) he presents to the air. Maybe adopting a running position that reduces this area, but that wouldn't reduce his performance/ability to deploy the power he actually does."
The researchers analyzed Bolt's 100-meter sprint in the 2009 World Championships in Berlin, where he set a new world record at 9.58 seconds. Considering Bolt's height (he stands six-foot, five inches), race-day conditions, and the speed he reached, the scientists calculated the amount of drag that Bolt had to overcome to set that record.
"The accurate recording of Bolt’s position and speed during the race provided a splendid opportunity for us to study the effects of drag on a sprinter," Hernandez said in a written statement.
What did the researchers find? Of the total energy that Bolt develops, only about 7.79 percent is used to achieve motion -- and 92.21 percent is absorbed by the fight against aerodynamic drag. With optimum wind conditions on that day, the researchers calculated that Bolt could have gone even faster -- crossing the finish line in an estimated 9.46 seconds.
“It is so hard to break records nowadays, even by hundredths of a second, as the runners must act very powerfully against a tremendous force which increases massively with each bit of additional speed they are able to develop," Hernandez said in the statement. “This is all because of the ‘physical barrier’ imposed by the conditions on Earth. Of course, if Bolt were to run on a planet with a much less dense atmosphere, he could achieve records of fantastic proportions.”
The research was published in the European Journal of Physics on July 25.