Speed is rarely the limiting factor in how fast you can race, even for a distance as "short" as the 5K.
There are many ingredients in the recipe of running fitness.
A mathematical model is designed to help runners pace their marathons appropriately.
Chances are you are slower over very short distance than your couch potato twin.
One study suggests that runners who rely on less muscle activation actually go faster.
A study finds that runners maintain their running economy despite losing speed as they age.