Speed limit: How fast can a human being run 100 meters?

A century ago, a time of 10.6 seconds in the men's 100-meter dash would have won an Olympic gold medal, and the very idea that a sprinter could run the 100 in under 10 seconds was seen as absurd. But at the 1968 Olympics, American Jim Hines eradicated that notion when he ran the 100 in 9.95 seconds. The world record has since been lowered to 9.58, a mark set by Jamaica's Usain Bolt in 2009.

As athletes continue to evolve and sports science develops, the time it takes humans to travel 100 meters is reducing, which leaves us pondering the age-old question: How low can it go?

Australian physiologist and sports scientist Jeremy Richmond says there are a number of new techniques sprinters are employing in an attempt to run even faster. In fact, he is confident the 100-meter record can be lowered below 9.3 seconds, possibly by the 2020 Tokyo Games.

One of the techniques Richmond cites is called plyometrics, also known as jump training.

"We now see a lot of athletes, especially the Jamaicans, doing hurdle drills to strengthen the hip flexion," Richmond said. "These hip flexion drills enhance the soleus muscle (lower calf), and studies show a strong correlation between the size of the soleus muscle and sprinting performance.

"A strong soleus muscle can play a significant role in acceleration over the first 10 meters, when the sprinter is at his slowest."

Another factor is that we could see more tall sprinters like Bolt, who is 6-foot-5, in the wake of his meteoric career. Richmond says Bolt's physical stature makes him the ideal sprinter prototype.

"Research suggests that if a sprinter is 10 percent taller, then he would have a 10 percent shorter ground contact time, which would allow him to run 10 percent faster," Richmond said. "However, the limiting factor with a taller sprinter is the energy it takes to bring the legs forward because of the longer limbs."

Despite Richmond's confidence that we will see faster times, limits exist.

"Without a doubt [the world record] can still get lower," he said. "If we can get the tallest sprinters to strengthen their hip flexors and the shorter sprinters to contract their muscles faster, then we should be able to see times around 9.27 seconds.

"It's certainly not possible for Rio, but maybe by Tokyo. Having said that, I doubt we'd really get past 9.2, because the loading involved at those speeds would force us to have super heavy bones, but then of course the weight becomes a negative factor."