Readiness Scores Explained: What Goes In and What They Miss

A readiness score is a daily summary of how recovered you appear to be. It combines overnight measurements such as sleep, heart rate variability, and resting heart rate with your recent training load and, in most apps, a short self-report, then compares each against your own recent baseline and produces one call for the day. It answers a narrow question: is today a good day to run the hard session as written, a smaller version of it, or something easy?

This guide covers what goes into a score, how the baseline that gives it meaning is built, and the things no score can see. The HRV guide and the resting heart rate, sleep, and load guide go deeper on the individual signals.

What a readiness score is for

Training plans are written weeks in advance by a calendar that knows nothing about last night. A readiness score exists to close that gap. It does not change what training you need. It changes when the demanding part happens, so that hard sessions land on days your body can absorb them.

That framing sets expectations. A score is a scheduling aid. It is not a diagnosis, a fitness test, or a permission slip to add work on a good day.

The inputs, and what each one contributes

Most readiness systems draw on the same handful of signals. Vitadel Run uses sleep, HRV, resting heart rate, recent training load, and a 10-second body check-in. Here is what each one measures and why it is there.

The training-load input deserves a note. Gabbett (2016) argued that injuries follow rapid spikes in load relative to what an athlete is used to, and proposed comparing the last week's load against the last month's, the acute-to-chronic ratio. A readiness score that includes load is watching for that spike. One that ignores load can read green on the morning after your biggest week ever.

Why everything is compared with your own baseline

A resting heart rate of 52 is high for one runner and low for another. HRV varies so much between people that a population norm is close to useless. Buchheit (2014) reviewed the heart-rate monitoring literature and concluded that most of its contradictions come from inconsistent measurement and from reading individual data against generic thresholds rather than against that person's own variation and measurement error.

So a readiness score builds a baseline first. It records your values for two to four weeks, computes your typical level and your typical day-to-day swing, and then judges each morning against that. A value one standard deviation below your normal means something. The same absolute value in someone else means nothing.

Two consequences follow for you. The score is provisional until the baseline exists. And the baseline has to keep rolling, because fitness changes it: Plews and colleagues (2013) describe resting heart rate falling and HRV shifting as elite athletes adapt to training. A baseline frozen in January will misjudge you in April.

How the inputs become a color

Most systems collapse the inputs into three states, because three states produce a decision and a number between 1 and 100 produces a debate.

The important design choice is that yellow shrinks a session rather than deleting it. Deleting sessions on every mediocre morning erodes the base that made the plan possible. Red needs a pre-decided replacement, such as 35 minutes of conversational running, because an open-ended decision made while tired usually resolves to nothing.

What a readiness score cannot see

The inputs describe your nervous system, your sleep, and your recent load. Several things that decide whether a season goes well are outside that.

• Tissue tolerance. Bone, tendon, and fascia do not show up in beat-to-beat intervals. A stress reaction can develop while every overnight signal looks excellent. The self-reported check-in exists to catch this, and it only works if you answer it honestly.
• Fueling. Under-eating suppresses recovery and performance. Its early signs are mood, cold intolerance, and changes in libido or menstrual cycle, none of which a wearable records.
• Heat and altitude. Both raise heart rate and lower HRV for reasons unrelated to training stress. A hot week or a training camp produces readings that look like overreach.
• Absolute fitness. A green day does not mean you can hold a faster pace than last week. Fitness comes from the training history. The score comments on the state you bring to it.
• Saturation in well-trained runners. Plews and colleagues (2013) describe HRV plateauing or falling even as resting heart rate keeps dropping and fitness improves. In that pattern an unusually high HRV can accompany deep fatigue. When the score and your body disagree at the extremes, follow your body.

When to override the score

Override a green reading when you have local pain that changes your stride, when you are ill with fever or chest symptoms, when you slept under five hours, or when easy pace has felt hard for three days running. Override a red reading when the cause is obvious and short-lived, such as one late night, and you feel fine after a warm-up. In that case start the session, run the first repetition, and decide from how it feels.

Sleep deserves its own line. Fullagar and colleagues (2015) reviewed sleep loss in athletes and found that some maximal efforts survive a short night while sport-specific performance tends to decline, and that restricted sleep can produce autonomic changes resembling overtraining. A week averaging under six hours is a week to hold volume regardless of what any single morning's score says.

What to do with the score over months

The habit that pays is measuring the same way every day and acting on trends rather than single readings. Foster (1998) found that illness in 25 athletes clustered when individuals exceeded their own thresholds of accumulated strain, not on any single hard day. A readiness score earns its keep when you look back after a training block and find that your hard sessions landed on your better days and your reduced weeks arrived before you needed them.

Vitadel Run builds the baseline from Apple Health and connected wearables, adds the morning check-in, and shows the drivers behind each day's color so you can see which input moved. The adaptive plans guide covers how a green, yellow, or red day should change the session without changing the plan.