Sentence:  Long popular in Europe, various forms of endurance sports are finding their niche on this side of the Atlantic as well. In addition to trail running, there is ultra running, wilderness running, mountain running and orienteering. Yet another offshoot gathering steam is <WSD>fastpacking</WSD> — running multiple days on the trail while carrying a pack with food and tent. 
Meaning of the word marked with <WSD> tags:  Running while carrying a backpack.