Methodology

How the scores work

Percentiles

For each normed test we look up the published reference row for your sex and age group, then place your result between the two nearest published percentiles using straight-line interpolation. If you're below the lowest or above the highest published percentile, we say so ("below the 10th", "above the 90th") rather than guess.

Ratings

Below 20th: Needs work · 20–39th: Fair · 40–59th: Average · 60–79th: Good · 80–89th: Very good · 90th+: Excellent. This follows the quintile framework proposed by Tomkinson et al. (2025), with a 90th-percentile "Excellent" tier added. For the chair stand at 60+, where only the 25th–75th percentile range is published, ratings are Below / Typical / Above range.

Strong After 40 Score (0–100)

The average of your percentiles across the normed tests you entered (VO2 max, grip strength, chair stand). For scoring only, results outside the published range count as the midpoint of the open band (e.g., below the 10th = 5, above the 90th = 95; for 25th/75th-only tables, below = 12.5, above = 87.5). Dead hang and ruck pace don't count because no validated norms exist.

The sources

FRIEND Registry (Kaminsky et al., 2022)

16,278 treadmill tests from apparently healthy US adults aged 20–89, 34 laboratories. Lab-measured VO2peak on a treadmill (cardiopulmonary exercise test). Smartwatch VO2 max values are estimates and can differ from lab values by several points.

Tomkinson et al., 2025 (2.4M adults, 69 countries)

2,405,863 adults aged 20–100+ from 100 studies, tested 2000 onward. Reference protocol: seated, elbow flexed, hydraulic dynamometer adjusted to hand size, 3 tries per hand, best single squeeze from either hand.

Rikli & Jones, 1999 (Senior Fitness Test, ages 60–94)

7,183 community-dwelling US adults aged 60–94 (267 sites, 21 states). Only the 25th and 75th percentiles (the "normal range") are used here. Scores below 25th or above 75th are reported as such, not as an exact percentile.

Rev Med Chile, 2025 (30s sit-to-stand, ages 18–80)

499 adults (287 women, 212 men) from six Chilean centres. Used only for ages 40–59 because the standard US norms (Rikli & Jones) start at 60. Small, non-US sample — treat as a rough guide.

Known limitations

• VO2 max norms are lab-measured (treadmill CPX). Watch estimates can differ by several mL/kg/min.
• FRIEND reports by decade, so every age from 40 to 49 shares one reference row.
• Grip norms are international and harmonized to one protocol. Your device and technique matter.
• Chair stand norms for 40–59 come from a small Chilean sample (n=499). Rikli & Jones (US, n=7,183) covers only 60–94, and we use only its published 25th–75th range.
• Leaderboards are self-reported and anonymous, with basic plausibility checks.