Fitness · topic 3 of 5
Test your CRF
Which test you are offered, and why it might not be the hard one
In the app
A short health screen runs before your first test. A beta-blocker, or a resting pressure at or above 180 over 110, and the six-minute walk is the only test offered. Cleared and training regularly, and the twelve-minute run is recommended instead. You can always pick another.
blocked at 180/110 or above
retest nudged at 8 weeks
Video walkthrough — Test Your CRF
In production, coming soon
Verve recommends a fitness test in two stages, and the order is the whole design. Stage 1 is a safety ceiling — three questions about medical supervision, chest pain or dizziness during everyday activity, and any cardiac event in the past six months. Any yes means talking to a doctor before an all-out effort, and no amount of training history can lift that. It is applied before anything else is looked at.
Stage 2 reads your recorded training, and all five checks must pass before a maximal test is recommended: trained within the window, 4 of 8 weeks carrying 3 or more training days, at least 2 hard sessions a week, one hard session in the last 14 days, and fewer than 2 consecutive quiet weeks. Where all five pass, Verve prefers to repeat your last test — comparing a 6-minute walk against a 12-minute run mixes method variance into what you would read as a change in your fitness.
Why tests don’t mix.A submaximal walk estimates your capacity from how your heart responds to easy work; a maximal run measures what you can actually do. The two carry different errors in different directions — a walk under-reads a fit person, a first maximal run under-reads a cautious pacer — so a change between test types usually reflects the tests, not your fitness. Verve flags a mixed history in the app and reads trends within one test type; when you retest, it offers your last test again for the same reason.
Retesting is every 8 weeks.VO₂Max adapts with a half-time of about 10–11 days and a dependable change takes on the order of 21 sessions, so a test before about 4 weeks usually returns your old number and teaches you only that you tested early. Eight weeks is also the window Verve reads your training over, so the two are the same span rather than two nearby ones.
Why the app shows two windows
The readiness card in the app carries one row measured overthree months and five measured over eight weeks. That is not an inconsistency. They answer different questions and come from different places.
The three-month row is the exercise guideline’s. ACSM defines “currently active” as habitual activity over the past three months, and that definition is used for one decision only: whether you should speak to a doctor before an all-out effort. It is a screening threshold, and screening thresholds are conservative on purpose.
The eight-week rows are Verve’s own, and they answer a physiological question instead: which test suits the training you have actually done. Eight weeks is chosen because that is roughly how long fitness takes to move by an amount a field test can detect (Hickson 1981). Neither number can stand in for the other. Borrowing the screening threshold to answer the physiology question is how an app ends up recommending a maximal run to someone who walked twice last month.
Hickson et al — Time course of adaptive responses of aerobic power, MSSE 1981
The classic time-course study of aerobic adaptation. VO₂Max rises with a half-time of roughly 10-11 days, and a reliable, measurable change takes on the order of 21 training sessions. This is why Verve sets its retest interval at 8 weeks and says nothing useful is likely before about 4: under a month there is usually no change to find, and a test that returns your old number teaches you only that you tested too soon.
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Bacon et al — VO₂Max trainability and HIIT, PLoS One 2013
Meta-analysis of VO₂Max trainability. At least 3 days per week is the standard inclusion criterion across the trials showing genuine gains, which is the figure behind Verve's regular-training check: 4 of your last 8 weeks carrying 3 or more days of 30 minutes at moderate intensity or above.
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Zheng et al — Short- and long-term detraining and VO₂Max, BioMed Research International 2022
Systematic review and meta-analysis of detraining. Roughly two hard sessions a week MAINTAINS VO₂Max; improving it requires more than that. Detraining is measurable after short-term cessation and plateaus somewhere between 30 and 90 days. Two findings, two uses: Verve asks for at least two hard sessions a week before recommending an all-out test, and drops back to the walk test after two consecutive weeks with no training — whatever your last result said.
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Garber et al — ACSM Position Stand on quantity and quality of exercise, MSSE 2011
The ACSM position stand on prescribing exercise. Its point about improvement is relative rather than absolute: raising fitness requires volume above the individual's OWN prior maintenance level, not above a population figure. So when Verve asks whether a retest is likely to show a change, it compares your last 8 weeks against the 8 before them, and never against anyone else.
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Zinner et al — Physiological responses to 9 weeks of incremental ramp testing, SJMSS 2023
Tracks the magnitude and time-course of physiological response across nine weeks of repeated testing — the window over which a retest can be expected to reflect something real rather than noise. Supports the 6-9 week span Verve's 8-week interval sits inside.
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How Verve decides which test to recommend
CommentaryTwo stages, and the order matters. STAGE 1 is a safety ceiling: three questions about medical supervision, chest pain or dizziness during everyday activity, and any cardiac event in the past six months. Any yes means seeing a doctor before an all-out effort, and no amount of training history can lift that — it is applied before anything else is considered. Five further questions about diabetes, blood pressure, cholesterol, smoking and family history do NOT block anything; combined with age and sex they decide whether a maximal effort warrants clearance first. STAGE 2 reads your recorded training, and all five checks must pass before a maximal test is recommended: trained within the window, 4 of 8 weeks carrying 3+ training days, at least 2 hard sessions a week, one hard session within the last 14 days, and fewer than 2 consecutive quiet weeks. If all five pass, Verve prefers to repeat your LAST test — comparing a 6-minute walk against a 12-minute run mixes method variance into what you would read as a change in your fitness.
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Why Verve uses two different windows
CommentaryThe app reads your training over two spans, and they answer different questions. THREE MONTHS is ACSM's definition of being habitually active — at least 30 minutes of moderate activity on 3 or more days a week — and it exists to decide whether you should see a doctor before exercising vigorously. EIGHT WEEKS is about physiology, not clearance: Hickson 1981 puts the half-time of VO₂Max adaptation at roughly 10-11 days with a dependable change needing on the order of 21 sessions, which places a meaningful retest at 6-9 weeks. Neither number can do the other's job. Using the 3-month figure as a retest interval would borrow a screening threshold to answer a question about how fast fitness changes, and would mean telling someone whose VO₂Max has measurably improved at 8 weeks to wait another month before looking. So Verve keeps both: 12 weeks for whether a clinician comes first, 8 for whether the number will have moved.
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The ten methods, and what each one costs you in accuracy
CommentaryCPET (★★★★★) measures VO₂Max directly by gas analysis — the only method here that is not an estimate. Treadmill/ACSM and Bruce protocol (★★★★) estimate from workload under supervision. Cooper 12-minute and 1.5-mile runs (★★★★) are maximal field tests: all-out effort, no equipment. The 6-minute walk (★★★) is submaximal and correlates around r=0.4-0.6 with true VO₂Max, so it reads low for the already fit — but it needs no heart rate, which makes it the reliable choice on beta-blockers. The Rockport 1-mile walk (★★★) is submaximal and more accurate (r≈0.88, Kline 1987) but needs a finish heart rate, so beta-blockers rule it out. HR ratio (★★★) infers from resting and peak heart rate. Wearable VO₂Max (★★) carries 7-16% error and under-reads fit people while over-reading unfit ones. Manual entry records a result measured elsewhere. Every one of these remains available in the app; the recommendation simply picks the one that fits your safety answers and your training.
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