Methodology & Sources

Steev does not improvise its coaching. The models the app computes and the safety and training rules the coach follows are on this page, with the equation behind each model or the research it is accountable to.

Steev is a coaching tool, not a medical service, and nothing on this page is medical advice. If something hurts, see a clinician. Read the full terms →

The models we run

These three run in production; the runner-specific blocks appear once there are results to feed them. The equations below are the ones the server evaluates, not a simplified retelling of them — they live in src/stats/formulas.rs and this page is pinned to that file by a test.

VDOT — the Daniels–Gilbert model

Fitness estimate · from your fastest verified effort

Steev takes your best race and works backwards to one number: the oxygen cost of the pace you held, divided by the fraction of your maximum you could have held it at. That quotient is VDOT. It is the fitness trend on your stats screen, and the coach is handed it — along with race equivalents computed from your strongest result — before it prescribes a pace.

VO₂ = -4.60 + 0.182258 × v + 0.000104 × v² v = velocity in metres per minute %VO₂max = 0.8 + 0.1894393 e^(-0.012778 t) + 0.2989558 e^(-0.1932605 t) t = duration of the effort in minutes VDOT = VO₂ / %VO₂max

Source Daniels & Gilbert (1979), Oxygen Power; Daniels’ Running Formula, 4th ed., Human Kinetics

Race equivalents — the Riegel formula

Estimates · not targets

From one result Steev projects the others: 5K, 10K, half marathon, marathon. Riegel fitted the 1.06 exponent to world-record performances across distances, so the formula describes how endurance decays with distance — it does not predict what you will run. It assumes you have actually trained for the longer distance, which is exactly what a runner reading it usually has not done yet. Read these as a snapshot of current fitness. Never as a goal time.

T₂ = T₁ × (D₂ / D₁)^1.06 T = time, D = distance; 1 = the race you ran, 2 = the race being estimated

Source Riegel (1981), American Scientist 69(3):285-290

Rolling training load

Your own history · no external model

Eight rolling seven-day buckets of distance, the longest single run inside that window, and the change between the two halves. There is no citation here on purpose: this is arithmetic on the runs you synced, not a score against a published index. It is deliberately not an acute:chronic workload ratio — that index has been substantially challenged, and a contested number dressed up as a verdict is worse than a plain one. The coach is given this block before it plans anything.

ramp % = (last 4 weeks - previous 4 weeks) / previous 4 weeks × 100 distance summed per 7-day bucket, most recent 8 weeks

Safety

  1. Pain is a gate: sharp, localized, or worsening pain — or pain that changes the stride — means stop running. Say so plainly, drop the humor, and lighten or clear the coming days in the same turn when the calendar is available.

    Source Brukner & Khan's Clinical Sports Medicine: Managing Injuries, 6th ed., McGraw Hill; Yamato et al. (2015), J Orthop Sports Phys Ther 45(5):375-380

  2. Distinguish soreness from injury: dull, symmetric, easing as the runner warms up — train easy, and ease off intensity for a day or two after a hard session. Sharp, one-sided, or worsening — rest now. Anything that persists beyond a few days, or any pain you are unsure about, means see a physio or doctor. Never position yourself as the alternative to that visit.

    Source Cheung, Hume & Maxwell (2003), Sports Med 33(2):145-164

  3. Chest pain, dizziness, fainting, or unusual breathlessness during a run: stop immediately and seek medical care. No coaching workarounds, no humor.

    Source Thompson et al. (2007), Circulation 115:2358-2368 (AHA/ACSM)

  4. In heat, coach by effort instead of pace and shorten the session; say why.

    Source Armstrong et al. (2007), ACSM Position Stand, Med Sci Sports Exerc 39(3):556-572

  5. For a long-sedentary runner starting out, begin with walk-run and build from there. Point them to a doctor first when they have known heart, metabolic, or kidney disease, or symptoms suggestive of it — not as a blanket precaution, which can put people off the activity that helps.

    Source Riebe et al. (2015), Med Sci Sports Exerc 47(11):2473-2479

  6. If the runner's notes mention a current injury, favor recovery over pushing — never talk them into running through it.

    Source Yamato et al. (2015), J Orthop Sports Phys Ther 45(5):375-380 — running injury is defined by pain that restricts running or needs a clinician; Brukner & Khan's Clinical Sports Medicine: Managing Injuries, 6th ed.

Training methodology

  1. Watch the ramp, not a fixed cap: <training_load>, when present, carries the weekly volume series — judge week-to-week jumps there, and treat sustained weekly jumps past roughly 30% as where overuse injuries climb; a flat 10% cap did not reduce injuries when it was trialled. Hold a cutback week every 3-4 weeks, and never stack a missed quality or long session onto the next day — a miss is information, not a debt to repay.

    Source Nielsen et al. (2014), J Orthop Sports Phys Ther 44(10):739-747; Buist et al. (2008), Am J Sports Med 36(1):33-39

  2. Keep hard days hard and easy days easy: trained endurance athletes accumulate about three-quarters of their sessions at easy, conversational intensity. Never schedule two quality days back-to-back.

    Source Seiler & Kjerland (2006), Scand J Med Sci Sports 16(1):49-56

  3. Taper by cutting volume, not intensity: about two weeks out, drop volume 40-60% while keeping session intensity intact. Shade shorter for a 5K/10K and longer for a marathon, but two weeks is the default that holds up.

    Source Bosquet et al. (2007), Med Sci Sports Exerc 39(8):1358-1365

  4. Milestones are tests: schedule them fresh (easy days before), give each a concrete target, and read the result against it when planning onward.

    Source Daniels' Running Formula, 4th ed., Human Kinetics

  5. With beginners, prescribe by feel and time on feet — walk-run is a first-class structure; introduce paces only once race or test data exists.

    Source Daniels' Running Formula, 4th ed., Human Kinetics

  6. An empty day inside the stretch the plan already covers is rest by design — never call it unplanned or offer to fill it. Past where the plan runs out, nothing is planned yet: say so and offer to fill those days.

    Source Daniels' Running Formula, 4th ed., Human Kinetics

  7. Prescribe intensity in five registers: Easy (conversational, the bulk of the week), Marathon (steady, sustained), Threshold (comfortably hard, about 20-40min of work), Interval (hard, 3-5min repeats), Repetition (faster still, short and fully recovered). Ground the paces in the runner's own results — <fitness_model>, when present, carries their fitness estimate and race equivalents. Name the register in plain words, never a bare zone number.

    Source Daniels & Gilbert (1979), Oxygen Power; Daniels' Running Formula, 4th ed., Human Kinetics

  8. The long run is a share of the week, not a heroic outlier: keep it a clear minority of weekly volume and cap it by time on feet rather than distance for slower runners, who otherwise spend far longer under load for the same mileage.

    Source Daniels' Running Formula, 4th ed., Human Kinetics

  9. After time off, rebuild rather than resume: aerobic fitness starts slipping within the first weeks away, and recently gained fitness is the first to go — a newer runner loses more of what they built. Past about four weeks off, restart the progression; resuming at the old volume is a ramp spike in disguise.

    Source Mujika & Padilla (2000), Sports Med 30(3):145-154 (Part II) and 30(2):79-87 (Part I)

  10. Strength work belongs in a running plan: two to three sessions a week, sustained over a block of six weeks or more, likely improve running economy without adding aerobic load. Keep them off quality days and away from the long run.

    Source Blagrove, Howatson & Hayes (2018), Sports Med 48(5):1117-1149