FTP and threshold: what they are, how to test, and how often to retest

Almost every number in a structured training plan hangs off one anchor: your threshold. For cyclists that is FTP, functional threshold power. For runners it is threshold pace. Get that anchor right and every zone and target below it falls into place. Get it wrong, or let it go stale, and you spend months training to numbers that no longer describe you. It is worth understanding what it is, how to test it, and how often to bother.

What threshold actually is

Your threshold is, roughly, the highest intensity you can sustain in a metabolic steady state, the effort you could hold for something around an hour before it runs away from you. It is the single most decisive number for time-trial-like efforts and sustained climbing, and it is the reference point the rest of your training is built on. Your easy zones, your tempo, your VO2 work are all defined as fractions of it.

That is why the anchor matters so much. Everything downstream is derived from it, so a single accurate number sets your whole system correctly, and a single stale one throws all of it off at once.

Your threshold is the one number your whole plan is built on. Test it honestly, and everything else takes care of itself.

How to test it without wrecking a week

You do not need a lab. A good field test gives you a number you can trust, provided you set it up properly.

• Arrive fresh. This is the one that ruins most tests. Take at least a couple of genuinely easy days beforehand, or you will measure your fatigue instead of your fitness and set every zone too low.
• Use a repeatable protocol. A common cycling approach is two maximal efforts of about eight minutes with recovery between, taking around ninety percent of the average. A single sustained twenty-minute effort, scaled down slightly, is another standard. The exact protocol matters less than using the same one each time so your numbers are comparable.
• Pace it evenly. Going out too hard and fading gives a lower, misleading result. Aim for an effort you can hold steady and just barely finish.
• Record the date and method. An anchor is only useful if you know how fresh and how recent it is.

How often to retest

More is not better here. A maximal test is itself a hard session that costs recovery, so you test when the number has plausibly moved, not out of habit. As a rule, every four to six weeks during a heavy build phase, when fitness is changing fast and a stale anchor quickly makes every target wrong, and more like every eight weeks, or only at block boundaries, during base or maintenance, when it is changing slowly. Across a season that is usually three to six formal tests, not a monthly ritual.

Between tests your anchor is not really frozen. A genuine best effort in training, or a new record up a familiar climb, is evidence too, and a good system will nudge your estimate along so your targets do not drift out of date for two months at a stretch. But when you want a confident reset, a proper test is what delivers it.

Let one number update everything

The beauty of anchoring off threshold is leverage. Retest once, and every zone, every session target, and every load calculation recomputes from the new value automatically. You are not hand-adjusting a dozen numbers. You are updating one, and letting the rest follow.

Train Fondo treats your anchor as a living estimate rather than a fixed constant. It tracks how current your threshold is, watches how your sessions feel against it, flags when a retest is genuinely due, and recomputes every zone and target the moment you set a new one.