Your plan in four answers
Set for May 16, 2027, about 29 weeks out.
- Distances
- 10 miles, Half marathon, Marathon
- Terrain
- Flat
- Taper starts
- May 4, 2027
Course
The Colfax Marathon course
Denver's city marathon, run along Colfax Avenue and through Sloan's Lake, passing through Empower Field at Mile High twice and finishing in City Park. The profile is close to flat by Colorado standards.
Read the full course notes
The altitude, at a little over 5,000 feet, is what makes the race hard for visitors rather than any feature of the course.
- Terrain
- Flat
- Distances
- 10 miles, Half marathon, Marathon
- Weather on race day
- Mid-May in Denver starts cold, often in the 40s, and warms quickly under strong high-altitude sun. Late-season snow and 70-degree afternoons have both happened, sometimes in the same week.
What to train for
Altitude adjustment and sun management for anyone arriving from lower ground.
Expect to give up meaningful time per mile compared with a sea-level race, and set the goal accordingly rather than chasing your flat-course pace.
Arrive either two days before or two weeks before, not in between.
Sample week
A sample Colfax Marathon training week
A week from the middle of the build, about six weeks out. Your plan sets the real distances and paces from your own fitness and adjusts them every week as you train.
- Monday
- Rest, or 20 minutes of mobility
- Tuesday Key session
- Intervals: 5 × 1 km at 5K to 10K effort, easy jog between
- Wednesday
- Easy run, 5–6 mi
- Thursday Key session
- Goal-pace run, 7 mi with 4 mi at race pace
- Friday
- Recovery run, 4 mi, or cross-train
- Saturday Key session
- Long run, 10–12 mi easy
- Sunday
- Easy run, 4 mi, then 6 relaxed strides
Your build to race day
Taper
Tapering for the Colfax Marathon
Start the taper ten to fourteen days before race day. Cut your weekly volume by about a third, then by half in race week, and keep a few short efforts at race pace so your legs stay sharp. The course is flat, so pacing decides the day: rehearse your goal pace in short segments during race week. With the race on May 16, 2027, your taper starts around May 4, 2027.
Also in Claude
Ask Claude for this plan
Add AthleteSpace to Claude once, then paste this prompt and put in your own numbers.
Build me a training plan for the Colfax Marathon (Half marathon) on May 16, 2027. I run [distance] a week, [days] days a week, easy pace [pace].
Colfax Marathon training questions
How long should I train for the Colfax Marathon?
Most runners give a half marathon twelve to sixteen weeks of focused training on top of an existing base. The plan above counts back from your actual race date, so if you have less time than that it builds the best plan the remaining weeks allow rather than pretending you have longer.
Is the Colfax Marathon course hilly?
Flat. Denver's city marathon, run along Colfax Avenue and through Sloan's Lake, passing through Empower Field at Mile High twice and finishing in City Park.
What is the weather usually like at the Colfax Marathon?
Mid-May in Denver starts cold, often in the 40s, and warms quickly under strong high-altitude sun. Late-season snow and 70-degree afternoons have both happened, sometimes in the same week.
When should I start tapering for the Colfax Marathon?
Start the taper ten to fourteen days before race day. Cut your weekly volume by about a third, then by half in race week, and keep a few short efforts at race pace so your legs stay sharp. The course is flat, so pacing decides the day: rehearse your goal pace in short segments during race week. With the race on May 16, 2027, your taper starts around May 4, 2027.
Do I need an account to get a Colfax Marathon training plan?
No. The plan above builds in your browser with no account, no email, and no card. Make a free account only if you want to keep it, log your runs against it, and have the coach keep adapting it as your training goes.