What is "skyrunning"

Skyrunning is an extreme sport of mountain running above where the incline exceeds 30% and the climbing difficulty does not exceed II° grade. The governing body is the International Skyrunning Federation. The sport comprises a number of different disciplines from the short, steep Vertical Kilometer to the more popular SkyRace and SkyMarathon. Ultra SkyMarathons are becoming increasingly popular as are short vertical SkySpeed races which includes skyscraper racing.