Foundation
Weeks 1–6
Dec 28, 2026–Feb 7, 2027
Set the routine, grow easy volume gradually, and finish each week with enough control to repeat it.
20-Week Colfax Marathon Training Plan
Denver, COMay 16, 2027
Start around December 27, 2026. The calendar below gives each phase a real date, then the course guidance shows where to make the build specific to Colfax Marathon.
Every mile of the Colfax Marathon is run above 5,000 feet. The course sits between 5,172 and 5,533 feet as it works through Denver's City Park, Sloan's Lake and downtown, starting at 6:00 a.m. on the east side of Ferril Lake. The terrain is gentle. The air is the difficulty.
- Race day
- May 16, 2027
- Start window
- December 27, 2026
- Runway
- 20 weeks
- Course
- Rolling Hills · Mostly Loop
- Plan choice
- Current training
Does this window fit your starting point?
Use the longer window to make the early build calmer, not to add five months of hard training. The plan should begin close to your current load, hold most running easy, and delay the biggest race-specific work until the middle of the cycle.
- You want a longer foundation phase before marathon-specific training.
- Your current mileage is steady but below the load you expect to carry later.
- You prefer gradual long-run growth with regular step-back weeks.
- You can sustain a five-month routine without turning every week into a peak week.
The 20-week Colfax Marathon calendar
These dates define the job of each phase. Your current mileage, recent longest run, experience, goal, and available days still decide the actual workouts inside them.
Build
Weeks 7–13
Feb 8, 2027–Mar 28, 2027
Extend the long run, introduce race-specific terrain, and keep recovery weeks on the calendar.
Peak
Weeks 14–17
Mar 29, 2027–Apr 25, 2027
Complete the most demanding race rehearsals and settle fueling, pacing, shoes, and clothing before taper begins.
Taper
Weeks 18–20
Apr 26, 2027–May 16, 2027
Reduce the load, keep familiar running in the week, and let the work from the previous four months show up on race day.
Make the window specific to Colfax Marathon.
Build general durability first. Add the race's hills, flat sustained running, downhill exposure, heat, or humidity in layers after the weekly rhythm is stable, then make the final long runs the most course-specific.
Read the full race guideHow to train for the Colfax Marathon
Train for the Colfax Marathon by building aerobic ceiling and by setting an honest altitude-adjusted goal. If you live near sea level, the 693 feet of climbing is not your problem; running 26.2 miles in air a mile up is. Plan for a slower goal pace than your flat-course fitness says you have earned.
In practice that means more volume at easy effort and fewer sessions chasing exact paces. Threshold work run by feel travels to altitude much better than threshold work run by watch. If you can get to elevation at all in the final block, even for a weekend, take it.
Two logistics that are really training. A 6:00 a.m. start means eating at around 3:30 a.m., so rehearse that breakfast on long runs rather than improvising it. And dry Colorado air pulls fluid out of you without the soaked shirt that normally warns you, so drink on a schedule instead of by thirst.
Colfax Marathon course facts
- Course
- Mostly Loop · Rolling Hills · Road/Pavement
- Elevation gain / loss
- 693 ft gain, 694 ft loss
- Highest / lowest point
- 5,533 ft / 5,172 ft
- Marathon finishers
- 2,917 in 2026 (mid-size field)
- Boston qualifier
- Certified Boston qualifying course
- Finishers running a qualifying time
- 2.5% in 2026
- Typical race morning
- 46°F at the start, 73% humidity, partly cloudy
- Race day high / low
- 68°F / 40°F on average
Let your current training decide the actual plan.
Current mileage, recent longest run, marathon experience, goal, and available days determine which plans rank first. After you choose and subscribe, Stride dates every workout through May 16, 2027.
20-week Colfax Marathon plan questions, answered.
When should I start a 20-week Colfax Marathon plan?
The 2027 Colfax Marathon is scheduled for May 16, 2027, so the 20-week window opens around December 27, 2026. Treat that as the outside edge of the window, then line week one up with the plan's normal weekly rhythm.
Is a 20-week plan long enough for the Colfax Marathon?
Use the longer window to make the early build calmer, not to add five months of hard training. The plan should begin close to your current load, hold most running easy, and delay the biggest race-specific work until the middle of the cycle. The course does not change the opening load you can handle, so choose from your current mileage and recent longest run before adding race-specific terrain.
How should I prepare for the Colfax Marathon course in 20 weeks?
Build general durability first. Add the race's hills, flat sustained running, downhill exposure, heat, or humidity in layers after the weekly rhythm is stable, then make the final long runs the most course-specific. Train for the Colfax Marathon by building aerobic ceiling and by setting an honest altitude-adjusted goal. If you live near sea level, the 693 feet of climbing is not your problem; running 26.2 miles in air a mile up is. Plan for a slower goal pace than your flat-course fitness says you have earned.
What if the 20-week Colfax Marathon window has already started?
Do not double weeks or cram missed mileage into the remaining calendar. Use your current mileage, recent longest run, experience, goal, and available days to choose a plan that can enter at an appropriate point while preserving the taper.
How does altitude affect the Colfax Marathon?
It is the defining factor. The Colfax Marathon runs entirely between 5,172 and 5,533 feet, and runners arriving from sea level should expect to run slower than their flat-course fitness suggests, especially after mile 18. There is no way to fix that inside a training block, so adjust the goal instead.
Is the Colfax Marathon a good Boston qualifier?
No. Only 2.5% of Colfax finishers ran Boston qualifying times in 2026, and 3.6% did in 2025. The course itself is gentle, with 693 feet of climbing across 26.2 miles, but the altitude takes back more than the profile gives. Choose a low-elevation race if a qualifier is the goal.
Put the 20-week window against your actual race.
Each page counts back from race day, maps the 4 phases to real dates, and applies the window to that course and its typical conditions.