4-Day Colfax Marathon Training Plan

Denver, COMay 16, 2027

Four runs per week for 18 weeks: two easy runs, one midweek aerobic run, and one long run. The schedule stays fixed; the guidance below shows how to choose terrain, rehearse conditions, and prepare for the Colfax Marathon course.

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.

See the full 18-week plan Read the full race guide

Race day: May 16, 2027
18-week window: Around January 10, 2027
Course: Rolling Hills · Mostly Loop
Peak week: 40 miles
Longest run: 20 miles

Your complete Colfax Marathon schedule

The 18-week window opens around January 10, 2027. Weeks one through 17 keep the normal Tuesday, Wednesday, Thursday, and Sunday rhythm. Only race week moves so the marathon lands on its actual weekday. If the window has passed, do not skip ahead or cram missed mileage into the time left.

Open any week to see all seven days. Week 1 is open to start.

1Week 1Foundation · 15 mi

Mon

Rest

Tue

Easy

3 mi easy run

Wed

Cross-training

30 min easy cross-training or mobility

Thu

Easy

3 mi relaxed aerobic run

Fri

Rest

Sat

Easy

3 mi easy run

Sun

Long run

6 mi long run, conversational effort

2Week 2Foundation · 17 mi

Mon

Rest

Tue

Easy

3 mi easy run

Wed

Cross-training

30 min easy cross-training or mobility

Thu

Easy

4 mi relaxed aerobic run

Fri

Rest

Sat

Easy

3 mi easy run

Sun

Long run

7 mi long run, conversational effort

3Week 3Recovery week · 15 mi

Mon

Rest

Tue

Easy

3 mi easy run

Wed

Cross-training

Rest or 20 min gentle mobility

Thu

Easy

3 mi relaxed aerobic run

Fri

Rest

Sat

Easy

3 mi easy run

Sun

Long run

6 mi long run, conversational effort

4Week 4Build · 19 mi

Mon

Rest

Tue

Easy

3 mi easy run

Wed

Cross-training

30–40 min easy cross-training

Thu

Easy

5 mi relaxed aerobic run

Fri

Rest

Sat

Easy

3 mi easy run + 4 relaxed strides

Sun

Long run

8 mi long run, conversational effort

5Week 5Build · 22 mi

Mon

Rest

Tue

Easy

4 mi easy run

Wed

Cross-training

30–40 min easy cross-training

Thu

Easy

5 mi relaxed aerobic run

Fri

Rest

Sat

Easy

3 mi easy run

Sun

Long run

10 mi long run; practice fluids

6Week 6Recovery week · 18 mi

Mon

Rest

Tue

Easy

3 mi easy run

Wed

Cross-training

Rest or 25 min gentle cross-training

Thu

Easy

4 mi relaxed aerobic run

Fri

Rest

Sat

Easy

3 mi easy run

Sun

Long run

8 mi long run, conversational effort

7Week 7Build · 25 mi

Mon

Rest

Tue

Easy

4 mi easy run

Wed

Cross-training

30–40 min easy cross-training

Thu

Quality

6 mi steady run; final 1 mi at planned marathon effort

Fri

Rest

Sat

Easy

3 mi easy run

Sun

Long run

12 mi long run; practice fuel and fluids

8Week 8Recovery week · 23 mi

Mon

Rest

Tue

Easy

4 mi easy run

Wed

Cross-training

30 min easy cross-training or mobility

Thu

Easy

5 mi relaxed aerobic run

Fri

Rest

Sat

Easy

4 mi easy run + 4 relaxed strides

Sun

Long run

10 mi long run, conversational effort

9Week 9Build · 29 mi

Mon

Rest

Tue

Easy

4 mi easy run

Wed

Cross-training

30–40 min easy cross-training

Thu

Quality

7 mi steady run; middle 2 mi at planned marathon effort

Fri

Rest

Sat

Easy

4 mi easy run

Sun

Long run

14 mi long run; use race-day fuel timing

10Week 10Recovery week · 24 mi

Mon

Rest

Tue

Easy

4 mi easy run

Wed

Cross-training

Rest or 25 min gentle cross-training

Thu

Easy

5 mi relaxed aerobic run

Fri

Rest

Sat

Easy

4 mi easy run

Sun

Long run

11 mi long run, conversational effort

11Week 11Build · 32 mi

Mon

Rest

Tue

Easy

5 mi easy run

Wed

Cross-training

30–40 min easy cross-training

Thu

Quality

7 mi steady run; final 2 mi at planned marathon effort

Fri

Rest

Sat

Easy

4 mi easy run

Sun

Long run

16 mi long run; rehearse fuel, fluids, and kit

12Week 12Recovery week · 26 mi

Mon

Rest

Tue

Easy

4 mi easy run

Wed

Cross-training

Rest or 25 min gentle cross-training

Thu

Easy

6 mi relaxed aerobic run

Fri

Rest

Sat

Easy

4 mi easy run + 4 relaxed strides

Sun

Long run

12 mi long run, conversational effort

13Week 13Peak week · 36 mi

Mon

Rest

Tue

Easy

5 mi easy run

Wed

Cross-training

30 min easy cross-training or mobility

Thu

Quality

8 mi steady run; middle 3 mi at planned marathon effort

Fri

Rest

Sat

Easy

5 mi easy run

Sun

Long run

18 mi long run; full race-day fueling rehearsal

14Week 14Recovery week · 29 mi

Mon

Rest

Tue

Easy

5 mi easy run

Wed

Cross-training

Rest or 25 min gentle cross-training

Thu

Easy

6 mi relaxed aerobic run

Fri

Rest

Sat

Easy

4 mi easy run

Sun

Long run

14 mi long run, conversational effort

15Week 15Peak week · 40 mi

Mon

Rest

Tue

Easy

6 mi easy run

Wed

Cross-training

30 min easy cross-training or mobility

Thu

Quality

9 mi steady run; middle 4 mi at planned marathon effort

Fri

Rest

Sat

Easy

5 mi easy run

Sun

Long run

20 mi long run; complete race-day rehearsal

16Week 16Taper · 26 mi

Mon

Rest

Tue

Easy

4 mi easy run

Wed

Cross-training

25 min easy cross-training or mobility

Thu

Quality

6 mi relaxed run; 2 mi at planned marathon effort

Fri

Rest

Sat

Easy

4 mi easy run

Sun

Long run

12 mi long run, controlled effort

17Week 17Taper · 18 mi

Mon

Rest

Tue

Easy

3 mi easy run

Wed

Cross-training

Rest or 20 min gentle mobility

Thu

Easy

4 mi relaxed run + 4 short strides

Fri

Rest

Sat

Easy

3 mi easy run

Sun

Long run

8 mi long run, conversational effort

18Week 18Taper · 8 mi + race

Mon

Rest

Tue

Easy

3 mi easy run

Wed

Rest

Rest or 15 min gentle mobility

Thu

Easy

3 mi easy run + 4 short strides

Fri

Rest

Sat

Easy

2 mi shakeout, or rest

Sun

Race

Marathon — 26.2 mi

Week	Mon	Tue	Wed	Thu	Fri	Sat	Sun	Run total
Week 1Foundation	Rest	3 mi easy run	30 min easy cross-training or mobility	3 mi relaxed aerobic run	Rest	3 mi easy run	6 mi long run, conversational effort	15 mi
Week 2Foundation	Rest	3 mi easy run	30 min easy cross-training or mobility	4 mi relaxed aerobic run	Rest	3 mi easy run	7 mi long run, conversational effort	17 mi
Week 3Recovery week	Rest	3 mi easy run	Rest or 20 min gentle mobility	3 mi relaxed aerobic run	Rest	3 mi easy run	6 mi long run, conversational effort	15 mi
Week 4Build	Rest	3 mi easy run	30–40 min easy cross-training	5 mi relaxed aerobic run	Rest	3 mi easy run + 4 relaxed strides	8 mi long run, conversational effort	19 mi
Week 5Build	Rest	4 mi easy run	30–40 min easy cross-training	5 mi relaxed aerobic run	Rest	3 mi easy run	10 mi long run; practice fluids	22 mi
Week 6Recovery week	Rest	3 mi easy run	Rest or 25 min gentle cross-training	4 mi relaxed aerobic run	Rest	3 mi easy run	8 mi long run, conversational effort	18 mi
Week 7Build	Rest	4 mi easy run	30–40 min easy cross-training	6 mi steady run; final 1 mi at planned marathon effort	Rest	3 mi easy run	12 mi long run; practice fuel and fluids	25 mi
Week 8Recovery week	Rest	4 mi easy run	30 min easy cross-training or mobility	5 mi relaxed aerobic run	Rest	4 mi easy run + 4 relaxed strides	10 mi long run, conversational effort	23 mi
Week 9Build	Rest	4 mi easy run	30–40 min easy cross-training	7 mi steady run; middle 2 mi at planned marathon effort	Rest	4 mi easy run	14 mi long run; use race-day fuel timing	29 mi
Week 10Recovery week	Rest	4 mi easy run	Rest or 25 min gentle cross-training	5 mi relaxed aerobic run	Rest	4 mi easy run	11 mi long run, conversational effort	24 mi
Week 11Build	Rest	5 mi easy run	30–40 min easy cross-training	7 mi steady run; final 2 mi at planned marathon effort	Rest	4 mi easy run	16 mi long run; rehearse fuel, fluids, and kit	32 mi
Week 12Recovery week	Rest	4 mi easy run	Rest or 25 min gentle cross-training	6 mi relaxed aerobic run	Rest	4 mi easy run + 4 relaxed strides	12 mi long run, conversational effort	26 mi
Week 13Peak week	Rest	5 mi easy run	30 min easy cross-training or mobility	8 mi steady run; middle 3 mi at planned marathon effort	Rest	5 mi easy run	18 mi long run; full race-day fueling rehearsal	36 mi
Week 14Recovery week	Rest	5 mi easy run	Rest or 25 min gentle cross-training	6 mi relaxed aerobic run	Rest	4 mi easy run	14 mi long run, conversational effort	29 mi
Week 15Peak week	Rest	6 mi easy run	30 min easy cross-training or mobility	9 mi steady run; middle 4 mi at planned marathon effort	Rest	5 mi easy run	20 mi long run; complete race-day rehearsal	40 mi
Week 16Taper	Rest	4 mi easy run	25 min easy cross-training or mobility	6 mi relaxed run; 2 mi at planned marathon effort	Rest	4 mi easy run	12 mi long run, controlled effort	26 mi
Week 17Taper	Rest	3 mi easy run	Rest or 20 min gentle mobility	4 mi relaxed run + 4 short strides	Rest	3 mi easy run	8 mi long run, conversational effort	18 mi
Week 18Taper	Rest	3 mi easy run	Rest or 15 min gentle mobility	3 mi easy run + 4 short strides	Rest	2 mi shakeout, or rest	Marathon — 26.2 mi	8 mi + race

This free plan is complete, fixed, and ready to use.

It begins at 15 miles per week, peaks at 40, and asks you to manage schedule changes and missed training yourself.

A Stride plan ranks from your running, then dates to race day.

Current mileage, recent longest run, marathon experience, goal, and available days decide which plans rank first.

Build My Plan

How to use this plan for Colfax Marathon

The mileage builds your engine. Your long-run route, pacing, fueling, and clothing rehearsals make that fitness specific to this race.

How 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.

Keep the plan honest. This free schedule contains no speedwork. Apply the course guidance through route choice and race rehearsal without turning easy days into extra workouts. If your goal calls for marathon-pace work, compare it with First Marathon Plus.

Match the terrain

Run part of your Colfax Marathon long-run mileage on terrain that rises and falls. Hold effort steady on climbs, let pace change, and practice cresting without surging.

Rehearse race morning

Mid-May race mornings in Denver run near 46F with humidity around 73% and partly cloudy skies, warming to an average high near 68F. The 6:00 a.m. start means a cold twenty minutes in the corral and a warm final hour. Train some long runs starting in the dark so the early alarm is routine by race week.

Prepare for the hard part

From about mile 20 along Colfax Avenue, when the altitude has taken more out of you than your splits show and the sun is finally up.

Check the starting line before you commit.

Beginner-friendly does not mean couch-to-marathon. Week one asks for four runs, 15 total miles, and a six-mile long run.

Fifteen miles in week one is close to the volume you already handle.
You can protect four run days most weeks, including a weekend long run.
Your priority is a steady first-marathon build without speedwork.
You can start around January 10, 2027 without forcing the early weeks.

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

Sources

Colfax Marathon questions, answered.

When should I start this 18-week Colfax Marathon plan?

The 2027 Colfax Marathon is scheduled for May 16, 2027, so the 18-week window opens around January 10, 2027. Weeks one through 17 keep the normal weekly rhythm and Sunday long run; only the final race week shifts to the event's actual weekday. If that date has already passed, do not compress 18 weeks of mileage into a shorter window.

How should I adapt the four-day plan for the Colfax Marathon course?

Run part of your Colfax Marathon long-run mileage on terrain that rises and falls. Hold effort steady on climbs, let pace change, and practice cresting without surging. 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.

Is four days a week enough to train for the Colfax Marathon?

Four run days can be enough when 15 miles in week one is not a sudden jump and you can protect the long run most weeks. This schedule builds to a 40-mile peak and a 20-mile long run. A runner chasing an aggressive time or already supporting more volume may fit a higher-mileage plan better.

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.

The same four-day schedule, shaped around the course ahead.

Choose your race for its current date, course profile, typical race-morning conditions, and specific long-run guidance.