What it is
One hour at threshold ≈ 100 points
- An easy long run can score few points even with lots of km
- A short quality session can weigh more than a “comfortable” jog
- So different workouts sit on the same scale
Behind the coach
The science that guides Runvia
The coach doesn’t invent numbers. It builds on established endurance ideas: how fitness grows, when load gets too aggressive, which paces make sense. Here’s the plain-language version — and the literature behind what Runvia actually computes, not a generic running-science library.
The building block of load
TSS — how “heavy” each run is
Training Stress Score (TSS) turns a run into load points: not just kilometres, but how hard it was relative to your threshold and for how long.
In Runvia
How we calculate it
We prefer the most reliable data you have: pace (with normalized pace when available), otherwise heart rate, otherwise perceived effort. Day by day, those points become Fitness, Fatigue, Form and ACWR.
TSS scale (Coggan / TrainingPeaks tradition): a shared way to measure session stress — not “weekly kilometres alone.” When pace/HR are missing, Runvia can use perceived effort (session-RPE, Foster et al. 2001) on the same scale.
Fitness and fatigue
Fitness · Fatigue · Form
From each day’s TSS points come two traces: one that builds fitness over time, and one that is recent fatigue. The difference tells you whether today feels fresher or heavier.
What they are
Three numbers, one simple idea
- Fitness — the base built from weeks of TSS (slower to move)
- Fatigue — recent TSS (rises and falls fast)
- Form — how fresh you are relative to that fatigue
Why
Know when to push or rest
Without this lens it’s easy to stack hard weeks, or show up to a race underbuilt. In Runvia (Premium) you see them in Today, and the coach uses them to adapt the plan.
Impulse–response model: Fitness and Fatigue from daily load (Morton, Fitz-Clarke & Banister, J Appl Physiol 1990); in-app language is Fitness / Fatigue / Form (CTL / ATL / TSB).
Sustainable load
ACWR — recent vs usual load
It compares recent load (from TSS) with what you’re used to. Spike too fast, and the chance of feeling overloaded (or stopping) goes up.
Below your usual
Room to build — but staying too low for too long can let fitness drift down.
In the sweet spot
Recent load lined up with your usual load: where most progress is sustainable.
A sharp jump
Volume or intensity rose quickly. Runvia flags the band and the coach tends to ease off.
Recent vs usual load (ACWR), uncoupled in Runvia (7 vs prior 21 days; Lolli et al., BJSM). Bands help spot load jumps; using ACWR to predict injury is contested (Impellizzeri et al., IJSPP 2020) — so the app talks about “load variation,” not clinical risk.
Paces and races
VDOT — your form in one number
From a best result (or a serious effort) we estimate your current fitness level. From that come realistic training paces and a finish estimate — not a wish, but what today’s form can support.
What it does
E · M · T paces and predictions
- E — easy pace, where you build without frying yourself
- M — marathon / long-race pace
- T — threshold pace, quality work
- Finish estimates for 5K, 10K, half, marathon (and trail with climb) when form is measured
Why
Train at your level
A “3:30 plan” without knowing if you’re near that level is mostly stress. Runvia derives paces from real form (PR or best effort), so coach and calendar speak the same language.
VDOT equations from Daniels & Gilbert (Oxygen Power, 1979) and paces in Daniels’ Running Formula (Human Kinetics). In Runvia, E/M/T paces come from measured form (PR or best effort), not goal time alone.
Hills and trail
Elevation — GAP and equivalent distance
Uphill, the same watch pace costs more. Runvia doesn’t ignore climb (D+): it adjusts pace and, for trail races, estimates what that course would be worth on the flat.
GAP
Grade-adjusted pace
Grade Adjusted Pace estimates what you’d run on the flat at the same effort. It helps compare hilly runs with flat ones and improves load (TSS) when an elevation track is available.
Climb
Trail race ≈ “flat-equivalent” km
For predictions and prep phases, metres of climb (and technical level) feed a flat-equivalent distance. So an ultra with lots of D+ isn’t treated like a flat road of the same GPS length.
Energy cost on climbs/descents: Minetti et al., J Appl Physiol 2002 (doi:10.1152/japplphysiol.01177.2001). Easy paces stay tied to fitness; trail race prediction accounts for climb.
Intensity
Heart-rate zones
Not every run should feel “a bit hard.” HR zones help keep easy days truly easy and put intensity where it belongs — so you recover and improve.
In Runvia
Zones and focus
Zones start from your max (and heart-rate reserve when available). After runs you see time in each zone — useful to spot too much “gray zone” or a healthy mix.
Why
Easy easy, hard hard
Many runners improve when most volume is light and hard sessions are few but clear. The coach keeps an eye on that balance when it proposes the week.
Zones derived from the Daniels / Pfitzinger tradition (contiguous product scale, not a verbatim quote). “Easy easy, hard hard” follows polarized distribution (Seiler, IJSPP 2010) that the coach uses as recent-week context.
Today
Readiness — how ready you are today
One glance: push, hold, or recover today? It combines recent load with how you feel — and, if you connect Health, also sleep, heart-rate variability and resting heart rate.
What you see
A concrete recommendation
In the Today hub (Premium), readiness isn’t an abstract score: it steers the day and gives the coach context before touching the calendar.
Why
The plan follows life
A short night, a heavy week, or fresh legs change what makes sense today. Better to adapt than chase a fixed spreadsheet.
Combines Form/TSB, load variation and (when available) wellness signals. Near race day, volume taper aligns with the tapering meta-analysis (Bosquet et al., Med Sci Sports Exerc 2007); durations by distance remain product choices.
From data to plan
How it reaches the coach
1 · Measure
Your real runs
Phone GPS, Strava, FIT/TCX files; with Premium also watch and Health data. Every run updates load, form and context.
2 · Interpret
Numbers you can understand
TSS, Fitness, ACWR, VDOT, GAP and readiness stay explainable. You and the coach see the same signals.
3 · Propose
Then you confirm
The coach suggests the week or a reschedule. No silent edits: you say yes on the calendar.
4 · Listen
Pain and fatigue
If you report pain or exhaustion, the coach tends to cut volume or intensity. That’s training caution, not a diagnosis.
Want the glossary next to the plans? See also Free & Premium or the FAQ.
References
Literature behind the in-app numbers
A short list: only sources that underpin formulas or rules already in Runvia (load, paces, zones, trail, taper). This is not a full running-science review — and it excludes medical guidelines: Runvia remains training help, not clinical advice.
- Morton R.H., Fitz-Clarke J.R., Banister E.W. Modeling human performance in running. J Appl Physiol 1990 · doi:10.1152/jappl.1990.69.3.1171 — Fitness / Fatigue (impulse–response).
- Coggan A. / TrainingPeaks — Training Stress Score, Normalized Power, Performance Management Chart — TSS scale and PMC used in the app.
- Foster C. et al. A new approach to monitoring exercise training. J Strength Cond Res 2001 · PubMed 11708692 — session-RPE / sRPE when pace or HR is missing.
- Foster C. Monitoring training in athletes with reference to overtraining syndrome. Med Sci Sports Exerc 1998 — weekly load monotony and strain.
- Lolli L. et al. Mathematical coupling… acute-to-chronic workload ratio. Br J Sports Med 2019 · doi:10.1136/bjsports-2017-098110 — uncoupled ACWR (7 vs prior 21 days).
- Impellizzeri F.M. et al. Acute:chronic workload ratio: conceptual issues and fundamental pitfalls. Int J Sports Physiol Perform 2020 · doi:10.1123/ijspp.2019-0864 — predictive limits; in-app “load variation,” not an injury predictor.
- Daniels J., Gilbert J. Oxygen Power (1979); Daniels J. Daniels’ Running Formula (Human Kinetics) — VDOT equations and E / M / T paces.
- Minetti A.E. et al. Energy cost of walking and running at extreme uphill and downhill slopes. J Appl Physiol 2002 · doi:10.1152/japplphysiol.01177.2001 — GAP / grade correction.
- Seiler S. What is best practice for training intensity and duration distribution in endurance athletes? Int J Sports Physiol Perform 2010 · doi:10.1123/ijspp.5.3.276 — polarization as coach context.
- Bosquet L. et al. Effects of tapering on performance: a meta-analysis. Med Sci Sports Exerc 2007 · doi:10.1249/mss.0b013e31806010e0 — volume taper approaching race day.
Other product choices (Friel zones, %HRR≈%VO2R equivalence, Tanaka max HR, and so on) stay in the internal spec. Here we only cite what explains the numbers you see in the app.
Important
Training help, not a doctor
Runvia guides you with data and running science. It does not diagnose, treat, or replace a healthcare professional — especially if you have specific health conditions.
Everyone responds to training differently. Treat coach and metrics as a compass, not the only truth. If you’re in pain, listen to your body and get help when you need it.
Try it on your running
Load, paces and readiness get useful when they talk about your runs.
