Jamaican super-sprinter Usain Bolt has accepted a challenge from British long-distance champ Mo Farah for a charity race later this summer at a distance somewhere in between the two runner's strengths.
Who would win? Science tells us that it depends on each runner's training and their strategy.
Bolt won gold at 100 meters and 200 meters at the London 2012 Olympics. Farah notched a double gold in the 5,000 meters and 10,000 meters before his home crowd last summer.
"It would be a fascinating, great race," said Roderick King, professor of sport and exercise biochemistry at Leeds Metropolitan University in England. "The two individuals are very different in biochemistry as result of their genotype and their training."
The 28-year-old Somali-born Farah has the body of a typical long-distance runner: thin (128 pounds), wiry (5-foot, 9-inches), and a lot of slow-twitch muscle that are adapted to endurance events. Bolt, 26, is massive in comparison: his six-foot-five inch frame carries 207 pounds across the track with fast-twitch, strength-producing muscles, according to King.
"What he can do is convert glycogen very quickly," King said about Bolt's ability to use the chemical compound of starch from food. "He's far superior at being anaerobic for fast reaction. As a consequence he can produce (energy) at rate that his muscle can use it. But he will fatigue."
Both runners share the same agent and the two are talking about racing after the summer international track and field season. King has reviewed the recorded times of both runners and predicts the two will be relatively equal at 550 meters.
But Bolt may be at a disadvantage because he carries more weight, said Jeffrey A. Potteiger, dean of graduate studies and professor of exercise physiology at Grand Valley State University in Grand Rapids, Mich.
"Obviously having more muscle and stronger muscle moves you faster across the ground," Potteiger said. "But you also have to move that mass, you have to carry that mass."
Potteiger said that while distance runners occasionally run short, fast spurts called intervals as part of their training regimen, sprinters tend to avoid any long distance training.
"If you start sprinting as a distance runner, you will recruit the muscles differently," he said. "If there is too much of that, those muscles start to get bigger."
Potteiger says that to find out who would win, it might make sense to treat the race like a chemical reaction -- using Bolt's times at 100, 200 and 400 meters to figure out at what point he would run out of gas.
"You could calculate the rate of decay of the reaction over time," he said. "That's what you are talking about with runner like Bolt."
For Farah, the idea would be to take a one-mile split time in the middle of a 5,000-meter race as a gauge of his pace. There's also each runner's own strategy:
"Mo is going to have to run faster than he normally would," Potteiger said, "and Bolt is going to have to hold back."