What a taper is actually for

Two weeks out from your race you do what everybody does. You cut your mileage. Big week becomes medium week, medium week becomes small week, and you keep the sessions, because the sessions are what keep you sharp.

Then race day arrives and your legs feel like someone else’s. Flat in the first hour. Nothing there when you go to lift the pace. You spend the next month wondering whether you tapered too much or too little.

Almost certainly neither. You very likely tapered the wrong thing.

What is happening underneath

A taper is not rest. Rest is what you do after the race. A taper is a controlled removal of fatigue while you hold on to the fitness underneath it.

Your form on any given day is roughly what you have built, minus what you are currently carrying. A training block adds to both sides. The fitness accumulates slowly and decays slowly. The fatigue accumulates quickly and, crucially, decays quickly too.

That difference in decay rates is the entire mechanism. Stop adding load and the fatigue drains away in one to three weeks while the fitness barely moves. What you are left with is most of what you built, carried by legs no longer buried under it.

A taper cannot make you fitter. It can only stop you arriving buried under the block that did.

There is nothing you can do in the last two weeks that will make you fitter on race day. There is a great deal you can do that will make you slower.

The mistake

Cutting volume is easy and it feels like discipline. You look at the plan, you take a third off, you feel virtuous. What almost nobody cuts is frequency and intensity, because those are the parts that feel like fitness. The interval session stays. The tempo stays. You just do them on shorter legs.

That is precisely backwards.

The fatigue you are trying to clear did not mostly come from the easy hours. Easy running is metabolically cheap and mechanically gentle. What is sitting in your legs on race morning came from the hard sessions, the fast running, the long descents, the strength work. Keep those in and cut the easy volume, and you have removed the part that was costing you least while keeping every part that was costing you most. You arrive at the start line rested in the sense of having run fewer kilometres, and still carrying most of the actual fatigue.

The correct shape is close to the opposite. Hold your frequency, keep running most days, drop total volume meaningfully, and reduce the hard work more than you reduce anything else, both in how often it appears and in how much of it there is.

Keep some intensity. Going completely flat for two weeks makes you feel sluggish and blunt. But keep a small amount of it rather than the same amount in a smaller container. The classic version is short, sharp and infrequent: a handful of race pace efforts, well short of what would normally be a session, spaced out, finishing well inside yourself. Enough to remind your legs and your head what the pace feels like. Not enough to leave a mark.

How long

Shorter races off shorter blocks need less taper. Long races off big blocks need more. A week to ten days for something in the half marathon range. Two weeks for a marathon. Two to three for a mountain hundred, where the fatigue you have built is deeper and slower to drain, and where arriving even slightly cooked costs you far more because you will be out there all day.

The individual variation around those numbers is bigger than most plans admit. Some people need a long taper and feel wonderful. Some go stale in ten days and race best off a short sharp one. Age matters, training age matters, and what you did in the block matters.

Which is why the useful thing to do is not to look for a better number.

Write down how you feel, this time

Your taper is a controlled experiment you will run maybe two or three times a year, and almost nobody records the result.

Note how you felt in the last ten days. Note the day the heaviness lifted, if it lifted. Note whether you felt sharp at day four and stale by day ten, or flat until day twelve and then suddenly good. Note what you actually did, not what the plan said.

Do that three times and you will know your own taper better than any generic prescription, because you will have three data points from the only athlete who matters. Do it zero times, which is what most people do, and you will be guessing again next year.

What it feels like when it is working

The middle of a taper is a strange and unsettling place, and knowing that in advance is most of the battle.

You will feel worse before you feel better. A few days after the volume drops, most people go through a patch of feeling heavy, sluggish and vaguely unfit. Legs feel odd. Easy pace feels like work. That is normal and it is not a sign the taper is failing.

You will also get twinges. Niggles you have not felt in months turn up during a taper with impressive reliability. Some of that is real. Some of it is that you finally have the spare attention to notice your own body. Treat genuinely new pain seriously and treat the tour of old grumbles with a bit of scepticism.

And you will feel like you are losing fitness. You are not. Not in two weeks. This is the single most common reason people sabotage a good taper by adding a session in the last week, and it is worth knowing in advance that the feeling is a liar.

The good sign, when it comes, has nothing to do with feeling fast. It is a familiar easy run suddenly feeling easier than it should for the pace. That is the fatigue draining out. If that has happened two or three days before the race, you are in good shape.

How we handle it, including the part we got wrong

The taper is shaped by cutting intensity and hard session frequency ahead of easy volume, for all the reasons above. Volume comes down, but it is not the first thing to move and it is not the thing that moves most.

There is also a check that a taper week can never carry more load than the training weeks it follows. That sounds obvious to the point of being insulting. It was not obvious to our first plan generator, which under some combinations of race distance and block length would produce a taper week that outweighed several build weeks, purely because the arithmetic allowed it. We found it, we wrote a test for it, and now a taper that exceeds what came before it fails a check rather than reaching a runner.

I mention it because it is the kind of error that is invisible when it goes wrong. A slightly too big taper week does not look wrong on a calendar. It looks like a normal week. You only find out on race day, and by then you will blame your legs.

Trailwise is not a medical device. Neither is it a replacement for a doctor or a physiotherapist. Trailwise flags what is worth a conversation. It does not diagnose, and it will tell you when it does not know.