Astrand-Ryhming step test VO2 max calculator
This Astrand-Ryhming step test VO2 max calculator estimates maximal oxygen uptake from a classic submaximal field protocol: a timed stepping bout at a known bench height and cadence, or an equivalent external work rate, together with the steady-state heart rate recorded at the end of the work.
Run — free
Coaches, exercise physiology classes, and wellness programmes use the Astrand-Ryhming approach when a full graded maximal test is impractical, yet they still need a numeric aerobic baseline that can be repeated after a training block. The engine applies the Buono closed-form of the Astrand nomogram with fixed sex-specific coefficients, multiplies by the classic Astrand age-correction factor when requested, and returns both absolute litres per minute and relative millilitres per kilogram per minute. Workload may be entered directly in kilogram-metres per minute or watts, or computed offline from body mass, step height, and steps per minute using the standard step-test mechanical factor. There is no network call, no random sampling, and no dependence on the current date. Use it free in the browser for personal tracking and classroom demos, or call the API at $0.002 per successful request when you need reproducible fixtures in coaching software, research pipelines, or automated wellness reports.
How to use it
Enter your values in the form above. The tool checks them before calculating and shows the result on the same page.
Check your inputs
Use the labels and units shown next to each field. If something is missing or outside the allowed range, the page points to the field to fix.
Use it again or automate it
Use the browser tool for individual checks and the API when you need the same capability in an automated workflow.
What you can do with it
Get an answer now
Enter one set of values and see the result without building a spreadsheet or script.
Compare scenarios
Change one value at a time and rerun the calculation to understand what affects the result.
Automate repeated work
Use the API when the same calculation needs to run inside your product or workflow.
FAQ
What does the Astrand-Ryhming step VO2 max calculator cost?
It is free in your browser on this page. Through the API a successful request costs $0.002; invalid inputs are not charged.
Which formula does this tool use?
The Buono et al. (1989) closed form of the Astrand-Ryhming nomogram: males VO2max L/min = (0.00212×W + 0.299)/(0.769×HR − 48.5)×100; females VO2max L/min = (0.00193×W + 0.326)/(0.769×HR − 56.1)×100, with W in kgm/min, optional Astrand age correction, and relative VO2 max = L/min×1000/weight_kg.
What happens if heart rate, weight, age, or workload is zero or negative?
The input is rejected with invalid_input. Non-positive values are not valid for the Astrand-Ryhming estimate.
Do I have to enter workload, or can I use step height and cadence?
Either works. Supply workload (kgm/min or watts), or omit it and the engine computes W from weight, step_height_cm (defaults 40 cm male / 33 cm female), and steps_per_min (default 22.5).
Is this a medical diagnosis of cardiorespiratory fitness?
No. It is a deterministic field-test estimate from published nomogram formulas and age factors. It does not replace graded exercise testing or clinical advice.
For developers — API access
Everything on this page is available programmatically. This section is for teams who want to wire it into their own systems; everyone else can just use the tool above.
API endpoint
Prefer to automate it? One authenticated POST creates the task; the result comes back by webhook or a signed link. The same capability also runs here on the web, by email and from Telegram — and soon from our app too.
Call it from your stack
curl -X POST https://api.kit.forhosting.com/health/vo2max-astrand-step \
-H "Authorization: Bearer $KIT_KEY" \
-H "Content-Type: application/json" \
-d '{"heart_rate":150,"sex":"male","age":30,"weight":70}'const res = await fetch("https://api.kit.forhosting.com/health/vo2max-astrand-step", {
method: "POST",
headers: {
"Authorization": `Bearer ${process.env.KIT_KEY}`,
"Content-Type": "application/json"
},
body: JSON.stringify({
"heart_rate": 150,
"sex": "male",
"age": 30,
"weight": 70
})
});
const { task_id } = await res.json();import os, requests
res = requests.post(
"https://api.kit.forhosting.com/health/vo2max-astrand-step",
headers={"Authorization": f"Bearer {os.environ['KIT_KEY']}"},
json={
"heart_rate": 150,
"sex": "male",
"age": 30,
"weight": 70
},
)
task_id = res.json()["task_id"]<?php
$res = file_get_contents("https://api.kit.forhosting.com/health/vo2max-astrand-step", false, stream_context_create([
"http" => [
"method" => "POST",
"header" => "Authorization: Bearer " . getenv("KIT_KEY") . "\r\nContent-Type: application/json",
"content" => '{"heart_rate":150,"sex":"male","age":30,"weight":70}',
],
]));
$task = json_decode($res, true);body := bytes.NewBufferString(`{"heart_rate":150,"sex":"male","age":30,"weight":70}`)
req, _ := http.NewRequest("POST", "https://api.kit.forhosting.com/health/vo2max-astrand-step", body)
req.Header.Set("Authorization", "Bearer "+os.Getenv("KIT_KEY"))
req.Header.Set("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)Example request
{
"heart_rate": 150,
"sex": "male",
"age": 30,
"weight": 70
}Example response
{
"task_id": "tsk_a1b2c3d4e5f6a1b2c3d4e5f6",
"type": "health.vo2max_astrand_step",
"status": "queued",
"_links": {
"result": "/tasks/tsk_…/result"
}
}The API is asynchronous: the call returns a task_id immediately and the result arrives by webhook. Polling is capped at 1 req/s per task.
Pricing
Published price — no tokens, no invented credits. A failed task is never charged.
Errors
| HTTP | Code | Meaning |
|---|---|---|
401 | unauthorized | Missing or invalid API key. |
402 | insufficient_balance | Your balance doesn't cover the task price. |
404 | unknown_type | That task type doesn't exist. |
429 | rate_limited | Too many requests. Use the webhook instead of polling. |