Endurance training, with the caveats left in.

Two time trials and one subtraction give you a swim pace you can train to the second. Here is the protocol, the math, the sets, and where the number stops being trustworthy.

The three signals are not competing versions of the same measurement. Here is what each one physically is, which session each should run, and what it means when they stop agreeing.

The training effect of a missed session is gone and cannot be bought back. The only useful question is what protects the rest of the week — here are the rules for one session, three days, and two weeks.

Normal training fatigue, functional overreaching, and overtraining syndrome are three different problems with three different fixes. Here is how to tell which one you have.

Four numbers run most endurance training software. Here is what each one measures, how to steer by them, and where they stop being trustworthy.

Periodization in plain English: pick the race that matters, build the year backward from it, and know what to do when the plan meets reality.

Tapering works because fitness and fatigue fade at completely different speeds. Here is how to use that gap, how long to take, and why you will feel awful halfway through.

The honest weekly hour ranges for every triathlon distance, split by whether you want to finish or to race, plus the floor below which a plan stops working.

Your device's threshold numbers are a real model fitted to your real data — and an extrapolation from efforts you may never have done. Here is how to tell which one you are looking at.

A plan that never changes is a forecast that stopped checking. Here is what a training plan should react to during a season, and the one change it should never make on its own.

Zone 2 is the effort you can hold for hours and still talk through. Here is what it does, how to find yours without a lab test, and where the popular version of the story overstates its case.