Running Glossary

Every term a runner needs to know — from your first 5K to a hundred-mile ultra.

1

10K

A race covering 10 kilometers (6.2 miles). Considered a middle-distance road race that rewards aerobic fitness and pacing discipline.

5

5K

A race covering 5 kilometers (3.1 miles). One of the most popular distances for beginners and competitive runners alike, typically completed in 15–45 minutes.

A

Aid Station

A staffed checkpoint along a race course providing water, sports drinks, food, and sometimes medical assistance to runners.

B

BQ (Boston Qualifier)

A finishing time at a certified marathon that meets the Boston Athletic Association's qualifying standard, earning entry into the Boston Marathon.

Bonking / Hitting the Wall

A sudden onset of extreme fatigue and energy depletion, typically around mile 18–20 of a marathon, caused by glycogen depletion. Prevented by proper fueling and pacing.

Bib

The numbered paper or fabric race number pinned to a runner's shirt, used for identification, timing chip placement, and finish-line photo matching.

C

Chafing

Skin irritation caused by repetitive rubbing of skin or clothing during running. Prevented with anti-chafe balm or moisture-wicking fabrics.

Chip Time

The official race time measured from when a runner crosses the start line to when they cross the finish line, recorded via a timing chip attached to the race bib.

Corral

A designated starting zone at mass-participation races, organized by projected finish time to allow faster runners to start ahead of slower runners.

Course Certified

A race course measured and verified by USA Track & Field (USATF) or equivalent body to meet distance accuracy standards required for record eligibility.

D

DNS

Did Not Start. Designates a registered athlete who did not begin the race, often due to injury, illness, or personal reasons.

DNF

Did Not Finish. Designates an athlete who started a race but did not cross the finish line.

E

Even Split

Maintaining a consistent pace throughout the entire race, so each half (or mile) takes approximately the same amount of time.

Elevation Gain

The total accumulated uphill climbing over a course. High elevation gain is a key difficulty indicator for trail and mountain races.

F

Fartlek

Swedish for 'speed play.' An unstructured training method alternating between fast and easy running, improving aerobic and anaerobic fitness simultaneously.

G

Gun Time

The elapsed time from the official start signal (gun) to the runner's finish. Differs from chip time for large-wave races where not all runners start simultaneously.

H

Half Marathon

A road race of 13.1 miles (21.1 km) — exactly half the marathon distance. A common goal race for runners building toward a full marathon.

L

Long Run

The week's longest training run, typically done at an easy conversational pace. The cornerstone of marathon preparation, building aerobic base and fat adaptation.

Lactate Threshold

The exercise intensity at which lactic acid begins to accumulate in the blood faster than it can be cleared. Training at or near this threshold improves race pace.

M

Marathon

The classic 26.2-mile (42.2 km) road race. Standardized in 1921, the marathon is the benchmark distance in competitive running.

N

Negative Split

Running the second half of a race faster than the first half. Widely considered the optimal pacing strategy for distance races.

P

Positive Split

Running the first half of a race faster than the second half. Often results in fatigue in the final miles.

PR / PB

Personal Record (PR) or Personal Best (PB) — the fastest time a runner has ever run at a specific distance.

R

Recovery Run

A short, easy run performed the day after a hard workout or race to flush metabolic waste and promote active recovery without adding training stress.

S

Strides

Short accelerations of 20–30 seconds at 90% effort, typically done after easy runs or before workouts to activate fast-twitch muscle fibers.

T

Tempo Run

A sustained run at comfortably hard effort — roughly marathon to half-marathon race pace — lasting 20–40 minutes. Builds lactate threshold.

Taper

The deliberate reduction of training volume in the 2–3 weeks before a goal race, allowing muscles to recover and energy stores to peak for race day.

Taper Madness

The psychological anxiety and phantom aches many runners experience during the taper period as they reduce training load before a race.

U

Ultramarathon

Any race longer than the marathon distance of 26.2 miles. Common ultra distances include 50K, 50 miles, 100K, and 100 miles.

V

VO2 Max

The maximum rate at which the body can consume oxygen during intense exercise. A key indicator of aerobic fitness and running potential.