u/Artificialcrafts26

Two years ago I ran my first marathon completely undertrained. Yesterday I ran my second one and the difference was night and day. Sharing this for anyone who just finished their first and is wondering whether a second one is worth attempting.

The first one was rough

I trained 4-5 months with no specific marathon plan. Just running 3 times a week, 70-90km total per month. The race itself was a night marathon around a lake in France, beautiful but tough. From km 25 onward I had bad stomach issues and the last stretch was pure survival mode. Finished in 4h22 at 6:11/km.

The week after I could barely walk. Legs, feet, ankles — everything hurt. I told myself never again.

What changed my mind

I joined an athletic club for triathlon and without really planning it, my running got properly structured for the first time. Coached interval sessions twice a week, one long zone 2 run on weekends, swimming twice a week for active recovery. No more junk miles, just purposeful work.

My diet changed too. I went from eating mostly carbs to properly balanced meals and noticed a real difference in energy levels during long efforts.

Second marathon prep

I kept my goal modest: just run under 6:00/km. Two long runs in March, 29km and 30km, then a taper week. Nothing fancy.

Race day

Felt good early and decided to push to 5:00/km and see how long I could hold it. Held it until km 35 where my quads started screaming. Slowed slightly and finished at 5:04/km average. 3h33 total.

No stomach issues this time. Recovered much faster than after the first one.

What I think made the real difference

Structured training through a coach rather than just logging miles. Cross-training through swimming that let me recover properly between sessions. Better nutrition. And honestly just knowing what the race feels like, the first marathon teaches you things no training plan can.

If your first marathon was brutal and you swore never again — I was exactly there two years ago. It genuinely gets better with structure.

I ran my second marathon yesterday and went from 6:11/km to 5:04/km in two years. The interesting part is that I didn't specifically train for the marathon. Triathlon training did most of the work and I want to hear if others have had the same experience.

Background

First marathon two years ago: purely running based, 3x per week, 70-90km/month, no structured plan. Finished in 4h22, suffered badly from km 25, spent a week barely walking afterward.

After that I joined an athletic club for triathlon. Completed my first Olympic distance triathlon 8 months later. The running component of my training shifted completely: two interval sessions per week coached by a club trainer, one long zone 2 run on weekends, two swimming sessions per week. Monthly running volume around 120km.

Second marathon prep

Honestly minimal marathon-specific work. Two long runs in March: 29km and 30km. That was essentially it on top of my usual triathlon training structure.

Result

5:04/km average. Quads started going at km 35 but held together. Nearly 70 seconds per kilometer faster than two years ago.

What I think actually drove the improvement

The coached interval sessions replaced what was previously just easy junk miles. Swimming twice a week allowed consistent training without the accumulated fatigue I had before. The overall aerobic base from multi-sport work seems to have transferred directly to running economy.

Has anyone here noticed their running improving significantly as a byproduct of triathlon training rather than running-specific work? Curious whether the structured intervals or the cross-training recovery aspect matters more in your experience.