Informs the optional resting-heart-rate VO2 estimate. The study used a morning, supine, five-minute HRrest measurement in well-trained men; even a protocol-matched input remains a rough estimate outside that narrow setting.
About & Methodology · Evidence reviewed September 10, 2026
Where the estimate comes from
Vitality Arc is a wellness estimator built from public formulas, published research, and product heuristics. It explores scenarios for cardio capacity. It has not been validated to predict healthspan or loss of independence.
Important context
Some parts of the app come from widely used public formulas. Other parts, especially future trajectories, reference-crossing times, and training scenarios, are product assumptions built for illustration. Associations in population studies do not establish a causal or individualized benefit.
Published formulas and measurement context
These sources inform the input methods. Any custom benchmark, extrapolation, or conversion beyond the original population is identified separately below.
Used when a user does not know their measured maximal heart rate.
Informs the MET values used for activity thresholds and readiness guideposts.
Supports the use of the Cooper test as a practical field estimate, while also highlighting that field tests carry more error than lab testing.
Measured adult treadmill reference data. The app does not reproduce the FRIEND percentile tables: its cardio guidepost curve is custom and is explicitly labeled illustrative.
What informs the guideposts
These papers and guidelines do not map one-to-one onto the whole product, but they inform how we think about cardio fitness, steps, strength, and general activity targets.
Adults: 150–300 moderate-equivalent aerobic minutes/week and muscle-strengthening involving all major groups on at least 2 days/week. Vigorous minutes count double and are optional. Older adults should also include multicomponent balance and strength activity on 3 or more days/week as appropriate to their abilities.
One of the reasons VO2max sits near the center of this estimator.
Supports grip strength as a useful optional strength input and explains why we treat it as a high-signal consumer metric.
Supports using daily steps as a practical everyday health signal.
Adds more support for daily steps as a practical movement signal.
Helps frame why grip is clinically interesting, but also why age context matters.
Longitudinal evidence that aerobic decline accelerates with age. It does not validate our exact yearly rates, the age-70 bend, or a person-level training-to-decline equation.
An observational study in male firefighters, not a validation of our push/pull composite. It does not establish female or general-population rep targets, a pull-up formula, or a causal benefit from adding repetitions.
A small middle-aged/older-adult validation found poor agreement and fitness-related bias. This is a limit on the heart-rate ratio method, not support for precise individual prediction.
Shows that measurement context matters: seated, supine, and sleeping heart rates differ at the population level and are not reliably interchangeable for an individual.
Evaluates sensor agreement against ECG during sleep. It does not validate conversion between the branded resting-heart-rate values shown in each app.
The Daniels-style race formula estimates VDOT, which also reflects running economy and endurance. The app labels it a proxy, not measured oxygen uptake.
Source of the optional lower-body test protocol and age/sex reference table, ages 60–94. The app does not make a fall-risk diagnosis.
Observational associations plateaued around 6,000–8,000 steps/day at ages 60+ and 8,000–10,000 below 60. The lower edges are guideposts, not individual minimums or reasons to reduce activity.
The 27 kg male and 16 kg female grip values are older-adult low-strength references. A single grip result cannot diagnose sarcopenia or determine future independence.
Adult categories apply from age 20. The reference interval is 18.5 to below 25; BMI does not distinguish fat from muscle and is not a stand-alone health assessment.
Adult central-adiposity categories apply with BMI below 35. The app does not grade body-fat percentage as healthier merely because it is lower.
What the app does not claim
Not a diagnosis
The app does not diagnose disease, screen for illness, or replace a clinician.
Not an exact lifespan prediction
The charts are meant to show plausible direction and reserve, not certainty about how long you will live.
Not lab-grade testing
Wearable data, field tests, and self-estimated inputs are useful, but noisier than direct clinical measurement.
Not finished science
This product will evolve as the underlying research review and calibration work improve.