About Mountain Running
Mountain Running is Athletics. Differences with Mountaineering, Orienteering and Skyrunning.
To distinguish the sport of mountain running from mountaineering or orienteering or skyrunning we can look at the philosophy of each sport.

The philosophy of mountaineering is based on contact with and challenge to nature. The time factor is only important in relation to our planning and safety. Climbers seek their adrenalin rush climbing on rock faces, looking for new routes and overcoming the danger inherent in their sport. A considerable amount of technical equipment, (ropes, pitons, etc) is needed. It is a question of combat between man and nature.

The philosophy of orienteering is to work out the quickest router between two points. Speed is important but it is useless without map-reading, compass, and route finding skills. In a few competitions, orienteering moves out of the forest, its natural habitat, and onto the mountains but its philosophy is still distinct from that of mountain running.

The philosophy of skyrunning seems to be an adventure on the mountain, trying extreme difficulties: in fact sky running is the discipline of running in the mountains above 2.000 meters, where the incline exceeds 30% and the climbing difficulty does not exceed II° grade. Ski poles and hands may be used to aid progress.

The philosophy of athletics, in our case mountain running, is based on the time factor, how to reach the finish taking the defined way as fast as possible. This is the objective of those who take part in competitive mountain running. Courses are designed to eliminate danger. No equipment is needed, no ropes, no compass. Athletes find their challenge in matching their speed against that of other runners, a competition between man (woman) and man (woman).
 
International Association of Athletic Federations (IAAF)
History
Mountain Running is Athletics.
Differences with Mountaineering,
Orienteering and Skyrunning.
Mountain Running Courses
What makes a Mountain Runner