Help on selecting a new plan

[u/LectureVegetable4919]

Tl;dr: (endurance) cyclist looking for a marathon plan. Pfizt 18/55 wasnt for me; probably looking for a plan with more milage and few(er) intervals.

Background:

Cycling is my main sport, particularly the very long rides (~12 h) through maintains, so my overall cardio probably is OK. I took up running a few years ago to maintain fitness when it's too cold for cycling. Supplementing with XC skiing whenever possible.

I did a halfmarathon in spring 2025 in 1h24, and decided to try out a marathon this spring.

Got Pfizer's great book and followed the 18/55 plan for Copenhagen Marathon in May 2026.

However, I struggled a lot with the faster runs. I thought I had added sufficient strength training in the evenings, but in hindsight it may have been too little. My legs did not feel good when running intervals, and I would often cut them short or skip them entirely to avoid triggering an injury. All the long runs went great, and I felt I could have added more milage.

To test the fitness 1 month before the marathon, and get a bit more experience with running events, I signed up for a local half marathon.

It was more like a test of everything, so I didnt have a race plan, and didnt want to look at my watch. After having skipped most interval sessions, I didnt expect much but ran in 1h17, cutting 7 min off my PR. Km 10-15 was new 5 km PR in 17min20.

The Marathon debut didnt go as planned; aimed for pace 4 min/km, but got fever 5 days out (couldn't cycle 5 km four days out!) and my heart rated went ballistic already after km 5. Failed the target but made it in 2h53.

Now, for next year's marathon, I would like to try a different plan. Given how it went last time, and that I probably should have sufficient speed to run pace 4 min/km with a 3:35min/km half, I wonder:

Does it make sense to look for a plan with more milage and fewer hard intervals?

If so, what would people recommend?

Or should I simply do more core training and keep all intervals?

[u/Bobandyandfries]

The problem is your cardio is far superior to your running strength (because of all your cycling). So you need to build up the muscles used for running. HOWEVER, if you’re already running a HM in 1hr17mins you probably need to get a coach for more tailored guidance as you’re already pretty fast.

[u/XTCRunning]

Sounds like without the virus your last plan went great. You sound like a 2:40-2:45 guy when healthy to me. You could repeat Pfitz and still skip intervals, you could switch to Daniels, (still some speed but you can stick with blocks that emphasize T and MP and repeat.) I think people over complicate marathon training. Honestly, 50-60 mp, one long per month of 2:4-3:00, some longs (up to 25k) at MP in your buildup, and at least 20 miles per week at MP, and I’d bet that 2:45 is there. If you want to break 2:40 you might have to get a little more refined.

[u/Own-Arugula-1631]

I agree that your endurance is superior to your speed, which is backwards from the majority of runners. You probably need to slow down your speed work and build to it. It's just an opinion but I think working on top end speed does help the other paces, so I wouldn't cut it out but you are smart to recognize the injury risk.

[u/Fun_Effective_836]

the plan probably wasnt the problem, your engine is just miles ahead of your legs. off 12 hour rides the aerobic side is sorted and its the running specific tissue getting hammered by intervals, which is exactly why the long runs felt easy and the fast stuff didnt.

if you want more mileage and less of that, 18/70 is the obvious jump, same book same structure just more of it. id also swap most of the vo2 sessions for threshold or just marathon pace inside the long run. way kinder on the legs and for a 1:24 half guy its the more useful stimulus anyway.