Long toes may give sprinters more speed
Research on sprinters suggests that runners with long toes and short heel bones could have an advantage over other athletes.
Sabrina Lee, a biomechanics researcher at Simon Fraser University, and Stephen Piazza of Penn State University compared ultrasound images of 12 college sprinters and 12 non-athletes.
They used these images to compare the subjects' toe lengths and examined how the Achilles tendon at the back of the heel slides during ankle motion.
The researchers found that the distance between the Achilles tendon and the centre of the ankle joint was shorter in the sprinters.
This is surprising because a longer distance between the tendon and the joint's centre of rotation would provide more leverage, the same way that it's easier to loosen a stubborn bolt with a long wrench than a short one.
The researchers said this apparent contradiction could be explained as a "tradeoff between leverage and muscle force-generating capacity." The greater the distance the tendon has to travel, the faster the muscle has to shorten, and muscle fibres that shorten quickly can't generate as much power.
Lee and Piazza developed a computer model to see how the acceleration generated by a foot changed when they altered the length of the heel bone and the toes.
"We found the greatest acceleration occurred when the Achilles tendon lever arm is the shortest and the toes are longest," said Lee.
Of course, foot shape alone doesn't make a sprinter, but the researchers say their work, published in the most recent issue of the Journal of Experimental Biology, shows how a unique configuration of bones can generate a burst of acceleration.
It's unclear if elite athletes are born with shorter heels and longer toes, or if these changes come about as a result of years of training.