The Metrics Decoder

The test to apply to every number below

A metric is only useful if it isolates you rather than the conditions.

Ask of anything on your dashboard: would this move if only the wind changed? If the answer is yes, it is not measuring you. That single question sorts most of a cycling dashboard into useful and decorative.

Load and freshness

Fitness

Is: roughly a six-week average of your daily training load.

Is not: a measure of how strong you are, or how much power you can sustain.

Do: watch it alongside your actual power. It drops during a taper by design, and during a few days off far faster than your capacity does.

Fatigue

Is: roughly a one-week average of recent load, and a proxy for how tired you are now.

Is not: a problem when it is high during a training block.

Do: expect it above Fitness during a block, and below it during a taper.

Form

Is: Fitness minus Fatigue. The freshness number.

Is not: meant to be positive during a training block.

Do: expect minus 20 to minus 10 in a block, and target plus 10 to plus 25 for an A race. Past plus 25 is stale rather than extra fresh. If your Form were positive in the middle of a block, that would be the actual problem, because it would mean you were not accumulating enough load to build anything.

Recent load against your established base

Is: what you asked of yourself in the last week, compared to what your body is actually prepared for.

Is not: a measure of how much you did. The risk lives in the ratio, not the total.

Do: respect the gap. A high load you built up to over months is manageable; the same load arriving suddenly is not, however fit you are. This is why five consecutive hard days catch experienced riders: recent load spikes long before your established base can rise to meet it.

Threshold and its relatives

Threshold

Is: roughly your best sustainable power for about an hour, and the anchor for every zone you have.

Is not: reliable if tested on tired legs. The standard 20-minute protocol also overestimates by five to ten percent for riders with high anaerobic capacity.

Do: if zone 4 feels maximal from the first rep and you cannot complete the prescribed volume, take five percent off and reassess in four weeks.

Critical Power

Is: a modelled physiological boundary, derived from the shape of your whole power curve.

Is not: interchangeable with threshold, and not convertible from it by a fixed percentage. The relationship is not a constant, and measured across real athletes it runs in both directions.

Do: use threshold to set your zones and critical power for pacing and analysis. Never use a percentage to get from one to the other.

Lactate threshold

Is: the intensity at which lactate production outpaces clearance. There are two of them: roughly 75 percent is the top of genuinely easy, and roughly 88 to 92 percent is the top of sustainable.

Is not: the point at which lactate appears. And lactate is not a waste product or the cause of burning legs. It is a fuel.

Do: treat your threshold figure as an estimate of the second one, and remember it can read high.

Indoor versus outdoor threshold

Is: two different numbers for the same body. Outdoor reads five to ten percent higher.

Is not: evidence that you lose fitness every winter.

Do: take your indoor threshold as roughly your outdoor number multiplied by 0.90. Climb-tested outdoor numbers need more like twelve to fifteen percent.

Reading a ride

Normalised power

Is: an estimate of the physiological cost of a variable effort.

Is not: average power with the zeros removed, and a bigger number is not a better ride.

Do: never use it to estimate your threshold, never to set zones, and never on efforts under about ten minutes.

Variability index

Is: normalised power divided by average power. A measure of how punchy the ride was.

Is not: a quality score. A club run sitting at 1.15 to 1.30 is exactly what a group ride looks like.

Do: read 1.00 to 1.05 as very steady, 1.05 to 1.15 as moderate, and 1.15 to 1.30 as punchy.

Decoupling

Is: how much your heart rate drifts upward across a steady-power ride.

Is not: a single-ride number. It is a multi-week trend.

Do: watch it fall across a base phase. It holds your output constant and measures the cost, which is why the conditions cannot hide in it.

Average speed

Is: a measure of wind, terrain, traffic, drafting and route.

Is not: a measure of you.

Do: stop using it to judge your training. A slow ride into a headwind at strong power is a good ride.

Weekly kilometres

Is: distance.

Is not: training load. Two 200 kilometre weeks can be entirely different training.

Do: count load, time in zone, or honest hours instead.

Your body

Heart rate variability

Is: the beat-to-beat variation in your heart rhythm, reflecting autonomic balance, and interpretable only against your own rolling baseline.

Is not: a recovery score, a fitness measure, a diagnosis, or comparable to anyone else's.

Do: treat one low day as noise. A low reading on a hard day softens that session. Four or more consecutive days means a recovery week now. Measure at the same time each morning, before getting up and before coffee.

Resting heart rate

Is: the steadier, less noisy companion to heart rate variability, and often the more useful of the two.

Is not: meaningful from a single morning.

Do: treat five to eight beats above your own baseline, across several consecutive mornings, as a sign that recovery is not keeping pace with load.

Sleep stages

Is: roughly 90-minute cycles, deep-dominant early in the night and REM-dominant late. Deep sleep drives growth hormone and tissue repair; REM drives skill consolidation.

Is not: proportionally reduced by a short night. Cutting sleep short removes the REM-rich hours almost entirely.

Do: keep a consistent wake time, which is a more powerful circadian anchor than an early night. Alcohol before bed eliminates most REM even when your total sleep time looks normal.

VO2max

Is: the size of your aerobic engine. The maximum rate at which you consume oxygen.

Is not: as trainable as advertised past the first few years. Expect 15 to 25 percent in an untrained first year, then one to two percent a year after three to five.

Do: once it plateaus, chase how much of it you can sustain rather than the ceiling itself.

Rider type

Is: a largely inherited muscle fibre ratio, visible in the shape of your power curve.

Is not: a limit on your development. Mitochondrial density is trainable to a far greater extent than fibre type or heart size.

Do: match your event calendar to your profile. Fighting it is slow and expensive; choosing around it is free.

Training design

Training zones

Is: a set of jobs. Zone 2 builds the aerobic engine, zone 4 raises threshold, zone 5 develops VO2max.

Is not: just a table of percentages. Two boundaries carry most of the meaning: about 75 percent is the top of genuinely easy, and about 90 percent is the top of sustainable.

Do: avoid both grey zones. 80 to 88 percent is easy rides drifting too hard. 95 to 104 percent is an interval landing between threshold and VO2max.

Polarised training

Is: roughly 80 percent of training time easy, 10 percent moderate, and 10 percent genuinely hard.

Is not: mostly easy with a bit of medium. Both ends have to be real.

Do: know that the advantage is clearest at high volume. Between eight and twelve hours a week, the evidence that it beats sweet spot is weak.

Sweet spot

Is: roughly 88 to 93 percent of threshold. High stimulus per hour at a manageable fatigue cost.

Is not: universally right. Accumulated across high volume it becomes chronic grey-zone fatigue.

Do: default to it under eight hours a week, and be careful with it over twelve.

Cadence

Is: a trade between muscular load and cardiovascular load.

Is not: something with a single correct value. Mechanically the most efficient is 60 to 70 rpm, while trained riders self-select 80 to 95 and are trading efficiency for faster recovery.

Do: ride at whatever cadence you sustain comfortably at your target power, and do not agonise over an arbitrary number.

Supercompensation

Is: the mechanism behind every adaptation. Stress, recovery, rebuild slightly higher, then decay if nothing follows.

Is not: a reason to worry about feeling worse after a hard session. That dip is the first half of the process.

Do: land the next hard session in the rebuild window, usually 48 to 72 hours later. Too early accumulates fatigue; too late detrains.

Durability

Is: the gap between your fresh power curve and your fatigued one.

Is not: captured by any fresh test, which is why testing predicts long events badly.

Do: aim to stay within five to eight percent. Past two hours, this decides the result rather than your threshold.

The five that matter most

If you track nothing else, track these.

1. Power at the same heart rate, rising
2. Decoupling, falling
3. Resting heart rate, trending down
4. Durability, within five to eight percent
5. Consistency, sessions completed against sessions planned

The fifth outranks the other four.