Marathon training with just an iPhone and Apple Health

What Apple Health actually gives you#

Apple Health is a data store on your iPhone that other apps and devices write into. Its practical significance for training is that it makes your hardware choice irrelevant: an Apple Watch, a Garmin, a Polar, a Coros, a Whoop or a chest strap paired to a third-party app all write into the same place.

For a marathon build, the relevant channels are:

Workouts — distance, duration, heart-rate series, pace, elevation, and route where the device recorded it
Sleep — duration and stages, from any device worn overnight
Heart-rate variability — usually an overnight average
Resting heart rate — typically the overnight low
Body mass, if you log it

That is enough to compute training load, fitness, fatigue, form and a daily readiness score. It is genuinely most of what a coaching platform reads.

What it does not give you#

Being straightforward about the gaps, because they are real:

Running power is not a standard Health type and mostly stays inside the vendor’s own ecosystem.
Lactate threshold from a lab test is not in there unless you put it there.
Structured workouts do not flow back out. Apple Health is a data store, not a workout delivery mechanism — an app that reads it cannot generally push tomorrow’s session onto your watch face. You read the session on the phone and execute it yourself.
Data quality is whatever your device recorded. A watch with poor optical HRV produces poor HRV in Health, and nothing downstream can fix that.

The workout-push gap is the one people miss most. If having intervals appear on your wrist matters to you, that is a genuine reason to stay inside a single vendor’s ecosystem.

Structuring the block#

A marathon build is 12–20 weeks depending on where you start. The structure that survives contact with reality:

Phase 1 — base, roughly half the block. Aerobic volume at low intensity. Boring, and it sets the ceiling on everything after it. Most of the running should be genuinely easy — conversational, and slower than feels dignified.

Phase 2 — build, roughly a third. Marathon-pace work and threshold sessions layered on the base. Volume plateaus; intensity rises. The long run gets specific: segments at goal pace rather than just distance.

Phase 3 — peak, two to three weeks. Sharpening. Highest-quality sessions, volume starting to trim.

Phase 4 — taper, two to three weeks. Cut volume 40–60%, keep intensity. Fatigue falls much faster than fitness does, so you arrive fresh on the base you spent months building.

Throughout: a recovery week every fourth week, planned in advance, not taken when you finally break.

The three numbers to watch#

Weekly volume growth. Keep it under about 8–10% week over week. This single constraint prevents more injuries than any other. Tendons and bone adapt far more slowly than the cardiovascular system, and the gap between the two is where most marathon builds fail.

Intensity distribution. Aim for at least 80% of your running time at low intensity. The characteristic failure of self-coached marathoners is not too little hard work — it is too much moderate work: runs done at an intensity high enough to accumulate fatigue but too low to drive adaptation.

Form, at race time. Arrive with fitness-minus-fatigue somewhere positive but not enormous. A very large positive number usually means you tapered too hard and lost sharpness. The guide to reading the chart covers this properly.

The long run#

The one session that most determines the outcome. Rules of thumb that hold up:

Build to somewhere between 30 and 35 km, or roughly 2:30–3:00 of running, whichever comes first. Time on feet matters more than distance for most people.
Do not run the full distance in training. The recovery cost outweighs the benefit, and you get the last 10 km for free on race day from the taper and the crowd.
Add specificity in the build phase: a long run with the final third at goal pace teaches something that a uniformly easy long run does not.
Practise fuelling in your long runs, in the exact form you will use on race day. More marathons are ruined by an untested gel than by inadequate training.

Fuelling#

Underfuelling is the single most common invisible problem in marathon training, and it looks exactly like overtraining: flat sessions, poor recovery, suppressed HRV, low mood, frequent minor illness.

The two things worth tracking:

Energy availability — what is left for basic physiological function after training is paid for. Chronically low availability is the mechanism behind most of what gets called overtraining, and it affects athletes of every gender.
Carbohydrate around hard sessions. The macronutrient that limits endurance training is rarely protein. High-load days need carbohydrate; easy days need less.

What this setup costs#

Approximately nothing, if you already own a watch. Apple Health is free and part of iOS. An app to read it and turn it into a plan may or may not cost something — several free and paid options exist, and the comparison pages cover the realistic choices including the ones that are cheaper than or free compared with Shindo.

What you do not need: a specific watch brand, a coaching platform subscription, a power meter, a lab test, or a second device to measure recovery.

Where this approach genuinely falls short#

You want workouts on your wrist. Stay inside one vendor’s ecosystem, or use a plan-delivery app that pushes to watches.
You want a human coach. No algorithm replaces one, and if you can afford a coach for a first marathon it is money well spent.
You are on Android. Apple Health does not exist there; the equivalent ecosystems are different and this guide does not apply.
You want deep power analysis. Cyclists in particular will find phone-based tooling limiting compared with a large screen.

Shindo reads Apple Health, computes readiness and training load on the iPhone, and builds a marathon block with phases, an 80/20 intensity split and an 8% ramp cap — and re-flows the block when you miss a week. The plan, the load charts and the workout detail are free.