Human performance: Scaling in athletic world records

World records in athletics provide a measure of physical as well as physiological human performance. Here we analyse running records and show that the mean speed as a function of race time can be described by two scaling laws that have a breakpoint at about 150–170 seconds (corresponding to the ∼1,000 m race). We interpret this as being the transition time between anaerobic and aerobic energy expenditure by athletes.