Running is one of the most efficient sports of all.
This is because there is hardly any other sport in which so many calories are burned as in running. While more intense sports, such as boxing or downhill skiing, burn more calories at the time of the activity than running, such high-intensity sports can't be done for nearly as long as running. A World Cup skier is usually on the slope for less than two minutes before reaching the finish line, whereas a marathon runner needs at least two hours (except for Eliud Kipchoge).