Most runners plan their training around a schedule. Far fewer plan it around how their body is actually coping that day — and that gap is where a lot of niggles, burnout and bad sessions come from. Three things the sports science literature keeps coming back to as genuinely useful signals are heart rate variability (HRV), rating of perceived exertion (RPE), and simple day-to-day wellness — sleep, soreness, stress and mood. None of them is a magic number on its own. Together, they’re a far better guide to today’s training than the plan you wrote three weeks ago.

This is also the thinking behind our free Running Readiness Score tool. Below is the research it’s built on, and further down, how to actually use it.

Why “how do you feel” is a real data point

It’s tempting to dismiss subjective wellness questions as soft or unscientific compared to a heart rate monitor. The research says otherwise. The Hooper & MacKinnon athlete wellness questionnaire, developed in 1995 and still widely used in applied sport science, asks athletes to rate just four things — sleep quality, fatigue, muscle soreness and stress — on a simple scale. Coaches and researchers have since found this short daily check-in tracks meaningfully with overreaching and drops in performance, often earlier than physical testing would catch it. A common extension used in team-sport monitoring adds a fifth item: motivation or mood, which tends to be one of the first things to dip when fatigue is accumulating.

The point isn’t that any single day’s soreness score means much on its own. It’s that a short, honest daily check-in, tracked over time, gives you an early warning system that a training log alone doesn’t.

RPE: the training load number that doesn’t need a lab

Rating of Perceived Exertion — how hard a session felt, on a simple scale — sounds almost too basic to be useful. But Carl Foster’s session-RPE method, which multiplies perceived effort by session duration, has repeatedly been shown to correlate strongly (in the region of 0.75–0.90) with more complex, heart-rate-based training load measures like Banister’s TRIMP. In plain terms: you don’t need a lab or a power meter to get a genuinely useful read on how much load a session put on your body. You largely already know, if you ask yourself honestly.

This matters because training load, not just training volume, is what your body is actually recovering from. A short, brutal interval session and a long, easy long run can carry very different “costs” even if the mileage looks similar on paper.

The workload-injury link

Tim Gabbett’s work on the acute:chronic workload ratio (ACWR) — comparing your recent week or two of training to your longer-term average — found that both doing too little relative to your recent history and spiking too hard both raise injury risk, with a ratio of roughly 0.8–1.3 generally considered the lower-risk “sweet spot,” and ratios above about 1.5 associated with a clear jump in injury rates. The practical takeaway for runners isn’t to obsess over the exact ratio — it’s the broader principle: sudden jumps in training stress, even well-intentioned ones (“I felt great, so I added a session”), are one of the more reliably identified injury risk factors in the research. Consistency beats enthusiasm.

HRV and resting heart rate: useful, but only against your own baseline

HRV and resting heart rate (RHR) get a lot of attention because they’re objective, wearable-friendly numbers. But the research from physiologists like Martin Buchheit and Laura and Paul Plews is consistent on one point that’s easy to miss: a single day’s HRV or RHR reading, in isolation, tells you very little. What matters is how today compares to your own rolling baseline over the past week or two. A resting heart rate of 52 might be completely normal for one runner and a clear red flag for another whose baseline sits at 44. Deviation from your personal norm — not the raw number — is the meaningful signal, and it typically takes several days of data before that baseline is stable enough to be useful.

This is also why HRV and RHR are genuinely optional in our tool, and why we don’t fold a single day’s reading directly into your score. They only start surfacing insights once you’ve logged enough days to have a real baseline to compare against.

Pain is different — and it overrides everything else

Wellness scores and training load are about optimising performance. Pain is a different category of signal entirely, and clinically it’s treated that way: the standard 0–10 Numeric Pain Rating Scale used across physiotherapy and sports medicine exists precisely because it’s a fast, reliable way to flag when something needs attention regardless of how good everything else looks. A great sleep score and low stress don’t cancel out a 7-out-of-10 pain reading. That’s the logic behind capping or overriding the readiness score whenever reported pain crosses a threshold — no amount of good wellness data should talk you into training through something that needs rest or a proper assessment.

How to use the Running Readiness Score

The tool takes under a minute and needs no login — your entries are saved privately in your own browser, not sent anywhere. Here’s how it works:

1. Open the Running Readiness Score page each morning, ideally before your session.
2. Answer the six quick check-in questions — sleep quality, fatigue, muscle soreness, stress, motivation, and yesterday’s training effort — on a simple 1–5 scale.
3. Rate any current pain from 0 to 10. Be honest here — this is the one input that can override the rest.
4. Optionally log resting heart rate and/or HRV if you track them. These aren’t required and won’t affect today’s score, but they’ll add useful context once you’ve logged a few days.
5. Hit calculate. You’ll get a score out of 100, a colour-coded zone (green through red), and a plain-language recommendation for the day.
6. Keep coming back daily. The real value isn’t any single score — it’s the trend line that builds up over time, showing you patterns your training log alone would miss.

A high score is permission to train as planned. A low one, especially with a pain flag, is your body asking for a smaller session, an easy day, or in some cases a proper assessment rather than another run. Either way, it’s a better starting point than guessing.

Try the Running Readiness Score now →

Sources

• Hooper & MacKinnon (1995) athlete wellness questionnaire — overview and original questionnaire
• Foster’s session-RPE and training load research — PMC review
• Gabbett, acute:chronic workload ratio — Science for Sport summary
• Plews & Buchheit, HRV-guided training — history and context and practical guide

This article and the Running Readiness Score tool are for general guidance and self-awareness, not a diagnosis or a substitute for professional advice. If pain persists or something feels seriously off, get it assessed.