Data was obtained from the HPI Health Profile Institute database, which includes Health Profile Assessments (HPAs) performed in the Swedish working population since the 1980-ies. An HPA includes a self-reported lifestyle questionnaire, anthropometric measurements, resting blood pressure evaluation, a submaximal cycle test, and concludes with a session with a health coach. HPAs are voluntarily accessible and free for employees in companies offering occupational health services. Historically, the Å-test, developed in the early 1960s, was the standard in HPAs. However, the EB-test, introduced in 2014, became an alternative in recent years.

For a contemporary study population mirroring current estimated VO2max levels, we included Å-tests and/or EB-tests from Swedish working individuals aged 20–69, conducted between 2010 and 2022. Out of a total sample of 481,815 men and women, a total of 370,880 had either performed an EB-test or an Å-test. Participants reporting intake of medicine that could affect heart rate response to physical activity were excluded. The resulting samples were for the Å-test n = 263,374 and for the EB test n = 95,043. As the output variables from the EB-test (sex, age, and heart rate response on the higher workload) can be used for calculation of estimated VO2max using the Å-test nomogram, n = 85,094 of the participants performing the EB-test also contributed with an estimated VO2max by the Å-test (Astrand and Ryhming 1954). See Supplement Figs. 1–3 for flowcharts.

The Å-test is based on measuring steady-state heart rate during the last minute of six-minute submaximal cycling on constant work rate (pedal frequency 50 rpm), aiming to obtain a rating of perceived exertion (RPE) of≈13 on the Borg’s scale (Borg 1970). VO2max is then estimated from a nomogram using workload, steady state heart rate, and sex, and further age-corrected (Astrand and Ryhming 1954; Astrand 1960). In a previous validation study, the mean (95%CI) difference between measured and estimated VO2max by the Å-test was -0.07 L/min (− 0.21 to − 0.06), and the coefficient of variance was 18.1% for men and women combined. Sex-specific analyses showed that men were being underestimated, 0.41 L/min (− 0.61 to − 0.20), coefficient of variance 14.8%, and women overestimated, 0.13 L/min (− 0.02 to 0.28), coefficient of variance 17.2%.

The EB-test uses the change in heart rate response between two four-minute submaximal workloads (pedal frequency 60 rpm), where cycling on a standard rate with a resistance of 0.5 kiloponds precedes a higher, individually chosen work rate to obtain an RPE of 13–14 on the Borg’s scale (Borg 1970). Mean heart rate values are calculated by measuring heart rate every fifteen seconds during the final minute of each workload. VO2max is estimated using the sex-specific prediction EB-test equations (Björkman et al. 2016). In a cross-validation study, the EB-test showed no significant difference on group level between measured and estimated absolute VO2max, mean (95% CI) of difference 0.02 (− 0.04 to 0.08) and coefficient of variance 9.4% for men and women combined (Bjorkman et al. 2016). Men experienced a small overestimation by the EB-test, 0.11 (0.02 to 0.20) and coefficient of variance 8.3%, and women a small underestimation, − 0.09 (− 0.16 to − 0.01) and coefficient of variance 10.0%.

Body mass and height measurements were acquired using standard methods, with individuals wearing lightweight clothing. BMI was determined using the formula: weight in kilograms divided by square height in meters (kg/m2). Exercise level was self-reported as weekly exercise frequency to maintain or improve physical fitness, health, using the following options: ‘Never,’ ‘Sometimes,’ ‘1–2 times/week,’ ‘3–5 times/week,’ or ‘At least 6 times/week,’ with individuals specifying their exercise frequency to maintain or improve physical fitness, health, and well-being. Exclusion criteria were smoking habits, categorized as ‘At least 20 cig/day,’ ‘11–19 cig/day,’ ‘1–10 cig/day,’ ‘Occasionally,’ or ‘Never.’ Only those reporting ‘Never’ were included. Additionally, self-reported medication usage for hypertension or those affecting heart rate and high blood pressure diagnoses were recorded as ‘yes’ or ‘no’.

The variables underwent visual normality inspection, revealing an approximation to a normal distribution. Consequently, we report the mean and standard deviation (SD). For analyzing differences between men and women, we employed independent t-tests. Additionally, to assess the effect size of these differences, we calculated Cohen’s d. Reference categories for relative estimated VO2max, segmented by 5-year age groups, were defined using percentiles: 0–10 (Very low), 11–25 (Low), 26–40 (Somewhat low), 41–60 (Average), 61–75 (Somewhat high), 76–90 (High), and 91–100 (Very high). Density plots were employed to provide smoothed probability density estimates, comparing the age-related distributions of the Å-test and EB-test in 10-year age groups. To explore associations between estimated VO2max and exercise and BMI, overall trends and percent of variance explained (R2) were used. These R2 values were derived from crude and sex- and age-adjusted generalized additive models with integrated smoothness estimation, utilizing five knots for the VO2max-BMI relationship. Additionally, crude and sex- and age-adjusted ordinary least squares regression was applied for the exercise-VO2max relationship.

The sample was divided into 10-year age groups (20–29, 30–39, 40–49, 50–59, 60–69) to assess the association with age. After that, the percentual difference between mean estimated VO2max of the current and the previous 10-year age group was calculated according to the following equation; (meanprevious decade − meancurrent decade)/meanprevious decade × 100 per decade.

All data handling, figures, and statistical analyses were performed with R version 4.2.0 Vigorous Calisthenics and the package tidyverse, and the flowcharts were made with the package dtrackr.