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Nature's Gym

The world of trail running has its own language. This can be both helpful and confusing to newcomers, so we created a short guide to help you understand the lingo.



  • Lugs: The sole of a trail running shoe has a series of lugs. “Luggy” helps to describe how rugged the lugs are on the trail running shoe.
  • Drop: Drop refers to the height difference between the toe and heel. It’s also called the “offset,” “ramp,” or “heel-to-toe drop.”
  • EVA: EVA (ethylene-vinyl acetate) is a lightweight, soft foam commonly used in a shoe’s midsole.
  • TPU: Thermoplastic polyurethane—TPU is commonly used as a stiff insert in the midsole for added protection. TPU can also be adapted to create a long-lasting, responsive midsole foam.
  • Rock Plate: A highly durable piece of material that protects your foot from rocks.
  • GORE-TEX™: A brand-name waterproof, breathable membrane. Many brands have a proprietary version of this as well.
  • Gaiter: A gaiter is a snug-fitting piece of material that protects your ankles and feet from debris.
  • Pronation: When your weight falls to the inside of your foot.
  • Overpronation When an inward rotation of the knee causes the ankle and foot to roll excessively inward.
  • Supination: When the outward rotation of the knee causes the ankle and foot to roll excessively outward (also known as underpronation).

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  • Vert: The vertical elevation gained in the ascent of a trail.
  • Out-and-Back: A trail that is linear and ends at the same location where you started. Typically, an out-and-back trail will have a scenic view in the middle.
  • Loop: A trail that loops around in a circular-like manner, starting and stopping in the same place.
  • K: Shorthand for kilometer.
  • 5K: A 5K run is a 3.1-mile run, walk, or hike.
  • Marathon: A marathon is a 26.2-mile run, walk, or hike.
  • Ultra: An ultra describes a run, walk, or hike with mileage that’s above 26.2 miles.
  • FKT: Short for fastest known time.
  • DNF: Stands for “did not finish.”
  • DFL: An initialism for dead freaking last.
  • Tempo Run: Also known as a threshold run. Tempo runs can be sustained or done in intervals. A tempo run should feel comfortably hard and be conducted at a pace that allows you to run for at least an hour. You want to go no higher than 85-90% of your maximum heart rate. To read more about tempo running and for other tips, check out Jack Daniels’ book Daniels’ Running Formula.
  • Fartlek Training: Fartlek is the Swedish term for “speed play.” Fartlek is typically unstructured and switches between hard, moderate, and very easy intervals. If you’re looking to better understand the differences between fartlek, tempo, and interval training, check out this Runner’s World article.

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  • Blaze: A mark that indicates the direction of the trail. It can be a pattern or a color. Be sure to follow the blaze that correlates with the trail you’re on.
  • Cairn: A mound of stones that may also indicate the direction of a trail.
  • Climb: To gain elevation—it often references a short, steep section of a trail.
  • Switchback: A bend in the trail that doubles back over the trail underneath it. A switchback makes otherwise-steep trails easier to run or power hike.
  • Scree: Very loose rocks that often span a field.
  • Rutted Out: A deep groove in a trail caused by erosion, wheels, or use.
  • Bushwack: To navigate a densely wooded grove or terrain.


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  • Gut Rot: The sensation that occurs when something you’ve eaten hurts your stomach.
  • Bonking: To hit a wall—experience fatigue, exhaustion, or lack of energy. Typically an indicator that you need more fuel or water.
  • Gel or Chew: A gooey or gummy substance high in calories that boosts energy quickly.
  • Bar: A calorie-heavy fuel source.
  • GORP: An acronym for “good old raisins and peanuts” or “granola, oats, raisins, peanuts.” Otherwise known as trail mix.


The more you trail run, the more likely you are to encounter new words or potentially even alternative meanings of the words we included here. Please feel free to comment or make a dictionary of your own!

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