A pacer is a runner who accompanies an ultramarathoner over designated sections of a race — usually the later, harder stages — to provide company, motivation, safety, and help with pacing and decision-making. Pacers don't run the whole race and typically may not carry the runner's mandatory gear or physically aid them beyond what rules allow. They're a common feature of 100-mile races.
A crew is the team of supporters — friends, family, or fellow runners — who meet a racer at designated crew-access aid stations during an ultra to resupply fluids and food, swap gear and clothing, provide encouragement, and help with problems. A good crew anticipates the runner's needs to make aid-station stops fast and effective, and is a major asset in long mountain races.
A drop bag is a bag of personal supplies that a runner packs in advance and the race transports to designated aid stations, where the runner can access it during the event. It lets runners resupply with food, fluids, dry clothing, lights, and gear at key points — especially valuable in ultras and where no crew is allowed. Smart drop-bag planning is an important ultrarunning skill.
An aid station is a designated checkpoint along a trail or ultra race that provides water, electrolyte drinks, food, and often medical support, drop-bag access, and a place for crews and pacers to meet runners. Aid stations let runners refuel and resupply, and managing them efficiently — getting in and out quickly — is a key race skill, especially in ultras.
A technical trail is one with rough, demanding terrain — loose rocks, roots, steep grades, drop-offs, stream crossings, and uneven footing — that requires careful foot placement, agility, and concentration. Technical terrain slows running pace, raises trip and injury risk, and rewards strength, balance, and good trail shoes; how technical a trail is strongly affects pacing and effort.
A vertical kilometer (VK) is a mountain-running race that climbs exactly 1,000 meters of vertical gain, traditionally over a course no longer than 5 km, making it extremely steep. A pure uphill test of climbing power and lung capacity, the fastest athletes summit in around 30–45 minutes, often power hiking the steepest pitches. It's a signature short, brutal discipline of mountain running.
Vert is trail-running shorthand for vertical gain — the total amount of elevation you climb over a run or race, measured in feet or meters. Because climbing is far more demanding than flat distance, vert is a key measure of a route's difficulty and a training metric; runners often describe routes and weeks by both distance and vert.
An FKT, or Fastest Known Time, is the fastest recorded time for completing a specific route or peak, set outside of organized races and verified by the community (often via GPS tracks). FKT attempts come in styles — unsupported (no outside help), self-supported (caches you set), and supported (a crew assists) — and have grown hugely popular as a flexible, race-free way to test fitness on iconic lines.
Ultrarunning (ultramarathon running) is running any distance longer than a standard marathon (26.2 miles / 42.2 km), most often on trails and in the mountains. Common distances include 50K, 50-mile, 100K, and 100-mile races, plus timed events. It emphasizes endurance, pacing, fueling, and mental resilience over speed, with strategies like power hiking and aid stations central to finishing.
Trail running is running on natural, off-road terrain — singletrack, dirt paths, hills, and mountains — rather than roads or pavement. It mixes running with elements of hiking on steep or technical ground, demands more agility, balance, and varied effort than road running, and ranges from short nature-trail jogs to mountainous ultramarathons.