Guides

What is training readiness, and can you trust the score?

Every recovery app now shows a daily readiness number. Here is what is behind it, why two apps disagree on the same data, and when to override it.

How to read fitness, fatigue and form (CTL, ATL and TSB)

Three curves explain most of what happens in a training block. Here is what each one means, what the numbers should look like, and how to use form to arrive at a race fresh.

Why is my readiness low when I slept well?

Sleep is one input among four. Here are the eight things that most often pull a readiness score down on a morning you feel fine, and how to tell them apart.

HRV for endurance athletes: what the number means, and what it does not

Heart-rate variability is the most useful and most misused number in endurance training. What it measures, why your absolute value is meaningless, and how to use it without becoming its hostage.

Marathon training with just an iPhone and Apple Health

You do not need a coaching platform subscription or a specific watch brand to train properly for a marathon. Here is what an iPhone plus Apple Health can and cannot do.

The 80/20 rule, the ramp cap, and why your plan should refuse you

The two constraints that prevent most self-coached failures are both refusals: keep 80% of training easy, and cap weekly growth. Here is the reasoning behind both.

Half-marathon training when the week doesn't go to plan

Most half-marathon plans assume twelve uninterrupted weeks, and almost nobody gets them. This is the other half of the problem: what should happen to the plan when a week goes missing, and what to do with the week after it.

Zone 2 without a lab test: what your own history already says

A lactate test gives you one number from one morning in a laboratory. Here is how to find the same boundary from the training already sitting in your history, and how far to trust it when that history is thin.

Why your watch's VO2max estimate moves, and what it actually means

Your watch said 52 last week and 49 today, and nothing about you changed in between. Here is how these estimates are produced, the six things that move them without any change in fitness, and the only way to read one usefully.

Heart-rate zones from your own data, not from 220 minus your age

The age formula hands you somebody else's zones. This is how to derive your own from a threshold you can find in the field, what to do while your history is still too short to say, and where heart rate is the wrong tool altogether.

One week of triathlon training on one iPhone

Three sports, one body, one recovery budget. Here is how to structure a self-coached triathlon week on a phone, and where a phone-only setup genuinely runs out of road.

Race week: what to change and what to leave alone

The final week cannot make you fitter, and it can absolutely make you slower. Here is the short list of what to change, the longer list of what to leave alone, and why the middle of the week feels awful.

Your pace lies in the heat and at altitude — here's the correction

Pace is an output, not an input. In heat, at altitude and on hills it stops describing effort, and comparing raw numbers across days quietly rewrites your training history.

What a weekly plan should do when you miss two sessions

A plan that only works when you follow it is a calendar. These are the five behaviours worth demanding of a weekly plan when life removes two sessions from it.