Denver Colfax Marathon

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Frequently asked

Glossary

1

Marathon (42.195 km / 26.2 mi)

The classic road-racing distance run over a measured course. At the Colfax Marathon weekend the full marathon is the headline event, with the course and start arrangements published on runcolfax.org before race day.

2

Half marathon (21.1 km / 13.1 mi)

Half the marathon distance and the most common step-up race for runners moving beyond 10K. Colfax weekend has historically staged multiple distances alongside the full marathon, so check runcolfax.org for the 2027 division list before you enter.

3

Marathon relay

A team format in which several runners each cover a leg of the marathon course and hand off at designated exchange zones. Relay teams need a team captain, a declared runner order and transport plans to and from exchange points, which are published by the organiser.

4

5K

A 3.1-mile road race that is usually walker-friendly and short enough to fit into a race-weekend schedule. It is the usual entry point for first-time racers and for families travelling with a marathon runner.

5

Bib

The numbered race document pinned to your chest or worn on a belt, carrying your timing tag and identifying you at start, aid stations and finish. Collect it at packet pickup with photo ID; never hand it to another runner.

6

Timing tag / chip

The disposable or reusable transponder attached to the bib or shoe that records net and gun times. Check that the tag is undamaged before the start and that your name and age group are correct in the results database.

7

Corral and wave start

Grouped start areas that release runners in waves so the field does not bunch up in the first kilometre. Your corral is normally assigned from the qualifying time you submit at entry; arrive early because gates usually close before the gun.

8

Qualifying / seed time

A recent official race time you submit so the organiser can place you in an appropriate start corral. Without a seed time you will typically be placed in a later, slower wave on race morning.

9

Pace team and pacer

Experienced runners carrying a sign at a fixed finish time, such as 4:00 or 4:30, to help others hold even splits. Pacers are a good option for first-timers at altitude, where an even effort matters more than a fast first mile.

10

Aid station

Course tables stocked with water, electrolyte drink and often gels or fruit, staffed by volunteers. Denver's dry air and mile-high elevation make it easy to under-drink, so plan to take fluids at more stations than you would at sea level.

11

Cutoff time and course closure

The clock limit after which roads reopen and course support ends. Cutoffs are set by the organiser and enforced at checkpoints, so confirm them before race day and choose a start wave that leaves enough margin.

12

Taper

The two to three weeks of reduced training volume before a race that lets the body absorb months of work. For a May Colfax weekend, the taper usually starts in late April, with sleep and hydration treated as part of the training plan.

13

Negative split

Running the second half of a race faster than the first. It is the standard advice for hilly or high-altitude courses, and it is far more comfortable on Colfax Avenue than going out hard and fading after the halfway point.

14

Personal best (PB) / PR

Your fastest verified time at a given distance. Denver races are usually treated as their own category because the altitude slows most sea-level runners by a noticeable margin, so many racers target a course-specific result.

15

DNF

Did not finish, the official result status when a runner leaves the course or misses a cutoff. If you stop, tell the nearest aid station or marshal so the timing team and medical volunteers can account for you.

16

Altitude and acclimatisation

Denver sits roughly 1,609 m (one mile) above sea level, where the air holds less oxygen. Arriving a day or two early, hydrating proactively and running by effort rather than pace are the standard adjustments for Colfax race weekend.

17

Race expo and packet pickup

The pre-race hall where runners collect bibs, timing tags and shirts and where brands, charities and physios exhibit. Hours and location are published by the organiser, and pickup usually requires photo ID plus your confirmation email.

18

Deferral or transfer

Moving an entry to another year or another runner under the organiser's rules, usually with a deadline and sometimes a fee. Ask before you book non-refundable travel, since deferral windows generally close weeks before race day.

19

Spectator zone

A designated area along the course where friends and family can watch safely without blocking runners or emergency access. On Colfax Avenue the pavement is shared with road closures, so spectators should follow marshal guidance and pre-arrange a meeting point.

20

Colfax Avenue course

The long arterial avenue that gives the race its name and forms the spine of the weekend. It runs east-west through Denver past City Park, so road closures and RTD detours affect both runners and anyone staying downtown.