Ready for a 2027 Marathon? The 5 Markers That Actually Matter

The question I get every October

Every year, around this time, excited athletes write to me: "Henri, I want to run my first marathon (or my next sub-4) in April. Should we start in January?"

My answer is never about the calendar. It's about the body they have today.

A 16-18 week marathon cycle doesn't build aerobic capacity from scratch — it exposes whatever is already there. If your base can't handle the volume and intensity you'll need by week 10, the cycle doesn't prepare you: it breaks you. I've seen it on the track and on the road, and I see it every season with my masters athletes: injury or stagnation doesn't come from the plan — it comes from starting the plan too soon.

That's why I use markers, not feelings. Here are the five I check before writing a single week of a marathon plan.

Marker 1: A sub-50-minute 10K, repeatable

I'm not talking about a 10K "run once, with a tailwind and fresh knees." I'm talking about being able to run that time (or better) two or three times in a month, under normal conditions, without it wrecking you for three days afterward.

This matters because a sub-50 10K reflects a combination of running economy and aerobic capacity that correlates directly with your marathon ceiling. The relationship between VO2max, lactate threshold, and endurance performance is well documented: performance at shorter distances reliably predicts performance at longer distances when the underlying aerobic base is solid (Joyner & Coyle, 2008). If your 10K time is still swinging 3-4 minutes between attempts, your aerobic system isn't stabilized yet — and a marathon cycle will amplify that inconsistency, not fix it.

What I'm looking for in the repetition: a time that doesn't depend on the day. A number that reflects fitness, not luck.

Marker 2: A half marathon under 2:00, also repeated

This is the marker I care about most, because the half marathon demands something the 10K doesn't: fuel management and connective tissue resilience under accumulated fatigue.

Running 21.1K in under 2 hours, and being able to repeat it, tells me three things:

1. Your lactate threshold sits in a place that allows you to sustain pace for more than 90 minutes.
2. Your tendons, fascia, and muscle insertions already tolerate time-on-feet roughly comparable to what a marathon will demand, doubled.
3. Your body has already metabolized, at least once, the transition from glycogen burning to fat burning under effort — something a marathon demands far more severely.

Consistency is the part most people overlook. One good half marathon can be race-day adrenaline. Two or three sub-2:00 halves in a season, across different workouts or races, is evidence of real, stable physiological adaptation.

Marker 3: Sustained weekly volume, not an isolated peak

I don't care about the one 70K week you ran three months ago. I care about your average over the last 8-12 weeks.

To seriously target a sub-4:00 marathon, I generally want to see a sustained average of 50-65K per week before starting the formal cycle — not as a goal for the cycle, but as the starting point. That gives the plan room to build toward peak weeks of 80-95K without the week-to-week percentage jump being brutal.

Evidence on exercise biomarkers reinforces this: physiological markers of adaptation to effort — inflammation, muscle damage, hormonal recovery — respond differently in bodies that already have an established aerobic base versus bodies that are just starting to build one [PMID:41922043]. A system that's already handling chronic load responds to acute stress more efficiently and recovers faster. A system without that chronic base interprets every heavy week as a crisis, not a stimulus.

Marker 4: Body composition and metabolic health, not just the number on the scale

This makes some people uncomfortable, but it's honest: the marathon is a test of sustained energy efficiency, and baseline metabolic health matters more than running culture likes to admit.

I'm not talking about ideal weight or aesthetics. I'm talking about your body already demonstrating the capacity to use fat as fuel during long efforts — which is trained primarily through low-zone aerobic volume, not through improvised calorie restriction halfway through the cycle.

There's relevant evidence from studies comparing high-intensity training modalities for fat loss: both cycling and running in HIIT format produce significant fat mass loss, but they also measurably alter gut microbiome composition [PMID:38233990]. This matters for the marathon runner because gut health is, in practice, the difference between tolerating gels and carbs on race day or suffering the dreaded "marathoner's gut" at kilometer 30.

Beyond that, general metabolic health — including hormone levels like testosterone in men — is linked to vascular capacity and recovery under chronic training stress [PMID:26590935]. It's not a marker you measure with a stopwatch, but it's something I discuss with athletes before starting a demanding cycle: does your body arrive with reserves, or does it arrive already depleted from other areas of life?

Marker 5: Cardiovascular recovery capacity between hard sessions

This marker rarely gets discussed, but to me it's decisive — especially for masters athletes (I'm speaking here partly from my own experience racing the 3000m in my 40s).

Before starting a marathon cycle, I want to see resting heart rate and heart rate variability (HRV) return to baseline within 24-36 hours after a hard effort. If your body takes 3-4 days to "come down" after a quality session, loading two hard sessions a week in January is going to generate accumulated fatigue that no plan — however well designed — can compensate for.

There's clear physiological support for this. Recent research on the cardiac effects of prolonged endurance exercise shows that both younger and older athletes experience measurable changes in cardiac function after long efforts, and that the capacity to recover that function varies significantly depending on baseline training level [PMID:40667749]. A heart trained for endurance adapts and recovers differently than one just beginning to be exposed to that stress — and a marathon cycle is, literally, months of repeated exposure to that stress.

As a side benefit, it's worth mentioning that sustained aerobic exercise is also associated with increases in brain-derived neurotrophic factor (BDNF), linked to better stress and anxiety management [PMID:25455510] — no small thing when you're facing week 14 of your cycle, legs heavy and your head starting to doubt.

How I use these 5 markers with my athletes

I don't require all five to be in perfect shape before starting. I require honesty about where each one stands. If you have 4 of 5 solid and one weak, we adjust the cycle — we don't cancel it, but we also don't pretend the problem doesn't exist.

What I never negotiate: sustained base volume (Marker 3) and cardiovascular recovery between sessions (Marker 5). Those two are the actual physical foundation. The 10K and the half marathon (Markers 1 and 2) are the reflection of that foundation, not the foundation itself. You can run one fast half marathon on sheer willpower. You can't fake an aerobic system that recovers well week after week.

Action plan for the next 10 weeks (through January)

1. Run a benchmark 10K this week or next. Write down the actual time, not the one "you know you can do."
2. Schedule a test half marathon (race or controlled workout) in the next 4-6 weeks. Repeat it if the first attempt doesn't give you the number.
3. Review your volume over the last 12 weeks, not just your best week. Pull the real average.
4. If you have a watch with HRV or resting heart rate tracking, start monitoring recovery after your quality sessions right now. December is the month to observe, not to ignore the signal.
5. Be honest about your overall metabolic health — sleep, stress, nutrition — before adding a marathon cycle on top of a life that's already running a deficit.

January arrives fast. But the body that starts the cycle in January was already built — or wasn't — in October, November, and December. That's the part of the work nobody sees on Strava, and it's the part that matters most to me as a coach.

References

• Siebers M, Bizjak DA. Exercise biomarkers. Adv Clin Chem. 2026. [PMID:41922043]
• Couvert A, Goumy L, et al. Effects of a Cycling versus Running HIIT Program on Fat Mass Loss and Gut Microbiota Composition in Men with Overweight/Obesity. Med Sci Sports Exerc. 2024. [PMID:38233990]
• Frandsen J, Aaroe M, et al. Cardiac Effects of Prolonged Endurance Exercise in Young and Older Athletes. Scand J Med Sci Sports. 2025. [PMID:40667749]
• Traish AM, Zitzmann M. The complex and multifactorial relationship between testosterone deficiency (TD), obesity and vascular disease. Rev Endocr Metab Disord. 2015. [PMID:26590935]
• Szuhany KL, Bugatti M, Otto MW. A meta-analytic review of the effects of exercise on brain-derived neurotrophic factor. J Psychiatr Res. 2015. [PMID:25455510]
• Joyner MJ, Coyle EF. Endurance exercise performance: the physiology of champions. J Physiol. 2008;586(1):35-44.