Resumo
Fitness age estimates how old your cardiovascular system is relative to population norms. A 45-year-old with excellent fitness might have a fitness age of 30, meaning their VO₂ Max (maximal oxygen uptake) matches the population average for a 30-year-old.
The concept was popularised by the NTNU Cardiac Exercise Research Group (CERG) in Norway. This calculator uses the Jackson et al. (1990) non-exercise prediction equation to estimate VO₂ Max, then maps the result to an age using population reference data.
Como funciona
- Estimate VO₂ Max — using your age, sex, BMI, and physical activity level (Jackson et al. equation)
- Optionally refine — if you provide your resting heart rate, the Uth et al. (2004) heart rate ratio method gives a second estimate, which is combined with the first using a harmonic mean
- Map to fitness age — your estimated VO₂ Max is compared against population average VO₂ Max values for each age, and the age where your VO₂ Max would be “average” becomes your fitness age
- Classify fitness level — your VO₂ Max is also classified against Cooper Institute norms (Very Poor to Superior) for your age and sex
The formulas
Jackson et al. (1990) — non-exercise prediction
Where
This equation was derived from over 2,000 participants and achieves a correlation of R ≈ 0.80 against laboratory VO₂ Max tests, with a standard error of approximately ±5 ml/kg/min.
Uth et al. (2004) — heart rate ratio (optional)
Where
When both estimates are available, they are combined using a harmonic mean: 2 × J × U / (J + U), which gives less weight to outlier estimates.
Physical Activity Rating (PAR) scale
| Rating | Description |
|---|---|
| 0 | Avoids walking or exertion |
| 1 | Walks for pleasure, uses stairs routinely |
| 3 | Light activity 1–2 days/week |
| 5 | Moderate activity 3–5 days/week |
| 7 | Vigorous activity 6–7 days/week, intense |
Exemplo prático
35-year-old male, 78 kg, 175 cm, moderate activity (PAR=5), resting HR 68 bpm
Calculate BMI
= 25.47
Jackson VO₂ Max estimate
= 44.42 ml/kg/min
Uth VO₂ Max estimate (with resting HR)
= 41.29 ml/kg/min
Combine via harmonic mean
= 42.79 ml/kg/min
Map to fitness age
= Fitness age: 26
Result
Fitness age = 26 (9 years younger than actual age of 35)
Entradas explicadas
- Age — your chronological age (18–80)
- Sex — biological sex; males have higher average VO₂ Max due to greater haemoglobin levels and cardiac output
- Weight and height — used to calculate BMI, which is an input to the Jackson equation
- Exercise level — maps to the Physical Activity Rating (PAR) scale. Higher activity → higher predicted VO₂ Max
- Resting heart rate (optional) — measured first thing in the morning before getting out of bed. A lower resting HR indicates better cardiovascular fitness. When provided, enables the Uth heart rate ratio method for a more refined estimate.
Resultados explicados
- Fitness age — the age for which your estimated VO₂ Max would be the population average. Lower than your actual age = fitter than average.
- Age difference — fitness age minus chronological age. Negative = younger, positive = older.
- Estimated VO₂ Max — your predicted maximal oxygen uptake in ml/kg/min. Elite endurance athletes typically score 60–85; sedentary adults 20–40.
- Fitness category — your VO₂ Max classified against Cooper Institute norms for your age and sex (Very Poor through Superior).
- BMI — your Body Mass Index, shown for context since it affects the VO₂ Max estimate.
Cooper Institute fitness categories (VO₂ Max, ml/kg/min)
Males
| Age | Very Poor | Poor | Fair | Good | Excellent | Superior |
|---|---|---|---|---|---|---|
| 20–29 | below 33.0 | 33.0–36.4 | 36.5–42.4 | 42.5–46.4 | 46.5–52.4 | above 52.4 |
| 30–39 | below 31.5 | 31.5–35.4 | 35.5–40.9 | 41.0–44.9 | 45.0–49.4 | above 49.4 |
| 40–49 | below 30.2 | 30.2–33.5 | 33.6–38.9 | 39.0–43.7 | 43.8–48.0 | above 48.0 |
| 50–59 | below 26.1 | 26.1–30.9 | 31.0–35.7 | 35.8–40.9 | 41.0–45.3 | above 45.3 |
| 60+ | below 20.5 | 20.5–26.0 | 26.1–32.2 | 32.3–36.4 | 36.5–44.2 | above 44.2 |
Females
| Age | Very Poor | Poor | Fair | Good | Excellent | Superior |
|---|---|---|---|---|---|---|
| 20–29 | below 23.6 | 23.6–28.9 | 29.0–32.9 | 33.0–36.9 | 37.0–41.0 | above 41.0 |
| 30–39 | below 22.8 | 22.8–26.9 | 27.0–31.4 | 31.5–35.6 | 35.7–40.0 | above 40.0 |
| 40–49 | below 21.0 | 21.0–24.4 | 24.5–28.9 | 29.0–32.8 | 32.9–36.9 | above 36.9 |
| 50–59 | below 20.2 | 20.2–22.7 | 22.8–26.9 | 27.0–31.4 | 31.5–35.7 | above 35.7 |
| 60+ | below 17.5 | 17.5–20.1 | 20.2–24.4 | 24.5–30.2 | 30.3–31.4 | above 31.4 |
Source: The Physical Fitness Specialist Certification Manual, The Cooper Institute for Aerobics Research, Dallas TX, revised 1997 (via Heyward 1998).
Premissas e limitações
- Non-exercise estimate only. The Jackson equation predicts VO₂ Max from questionnaire data with a standard error of ±5 ml/kg/min. A laboratory cardiopulmonary exercise test is the gold standard.
- The Uth heart rate ratio (15.3 coefficient) was validated on well-trained men aged 21–51 only. It may overestimate VO₂ Max for women, older adults, and untrained individuals. The calculator mitigates this by blending Uth with the Jackson estimate via harmonic mean.
- Population reference data is approximate. The VO₂ Max-to-age mapping uses values derived from ACSM and HUNT study norms, which represent Western populations and may not apply equally to all ethnic groups.
- Activity self-assessment is subjective. The PAR scale relies on honest self-reporting, which can introduce bias.
- Fitness age is not a clinical diagnosis. It is a motivational tool that contextualises VO₂ Max in an intuitive way.
Verificação
| Test case | Input | Expected VO₂ Max | Expected Fitness Age | Source |
|---|---|---|---|---|
| Active male | 35yo M, 78kg, 175cm, PAR=5, RHR=68 | 42.79 | 26 | Jackson + Uth harmonic mean |
| Sedentary female | 50yo F, 70kg, 165cm, PAR=3 | 23.69 | 64 | Jackson only |
| Very fit male | 25yo M, 85kg, 180cm, PAR=7, RHR=55 | 52.23 | 18 (clamped) | Jackson + Uth harmonic mean |
All values verified against manual calculation of the Jackson et al. (1990) and Uth et al. (2004) equations.
Sources
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