Long distance running requires a lot of stamina and mental strength. Some people say it is relaxing.
How can it be relaxing? 
Well, humans are well adapted for running significant distances so I think once someone does it for a while they get use to it and it becomes something they like to do.
How does it help one mentally? I could use some help, I have mommy brain.
Long-distance running
Long-distance running, or endurance running, is a form of continuous running over distances of at least 3 kilometres (1.8 miles). Physiologically, it is largely aerobic in nature and requires stamina as well as mental strength.
Among mammals, humans are well adapted for running significant distances, and particularly so among primates. The endurance running hypothesis suggests that running endurance in the genus "Homo" arose because travelling over large areas improved scavenging opportunities and allowed persistence hunting. The capacity for
- An individual sport
- A team sport (see relay race)
- A form of travel
- Animal locomotion
- Terrestrial locomotion
Forms of running.
- Backward running
- Barefoot running
- Sprinting
- Jogging
- ChiRunning
- Level and Incline Running
- Long-distance running – form of continuous running over distances of at least five kilometres (3.1 miles). Physiologically, it is largely aerobic in nature and requires stamina as well as mental strength.
Forms of running Running