I love long distance running. A person runs over a distance that covers  8 kilometers
What kind of distance race ?
Do you know Roger Banister?. Distance runs are usually aerobic in nature as you have to be a strong person to cover the distance in the time .
How do you mean aerobic ,is it a type of dance?
The type of run at the Olympics. Human beings have been designed to handle running the distances they can endure even better than other primates
Who are the primates ,are they animals?
There is a theory that says travelling and running long distances improves hunting abilities 
OK ,so human abilities that relates to primates you mean
endurance running is also found in migratory ungulates and a limited number of terrestrial carnivores, such as bears, dogs, wolves and hyenas.
In modern human society, long-distance running has multiple purposes: people may engage in it for physical exercise, for recreation, as a means of travel, for economic reasons, or for cultural reasons. Long distance running can also be used as a means to improve cardiovascular health. Running improves aerobic fitness by increasing the activity of enzymes and hormones that stimulate the muscles and the
“fartlek training allows you to add an endless variety of intervals to your aerobic workouts, which helps to keep you stimulated." A great plus to performing this workout is the variety it adds to fitness regimens; it is possible to change the amount of distance, time, fast bursts, recovery periods, and even the time at which you do each component.
Benefits Race day readiness.
For competitive runners, fartleks and all other types of interval runs are the key for race day readiness. The alternating speeds that