The test
Grip strength
How hard you can squeeze stands in for whole-body strength better than any other single measurement, and it starts falling earlier than most people expect.
What you need. A hand dynamometer. A reading from a gym or a clinic is fine.
How to do it
Doing it properly
- Sit with your elbow at your side and bent to a right angle.
- Squeeze as hard as you can for about three seconds.
- Three attempts each hand, resting between them.
- Record the best reading from your dominant hand.
What counts
The single best reading in kilograms, dominant hand.
What most people get wrong
- Swinging the arm or bracing against the body.
- Recording an average rather than the best attempt.
- Using a different dynamometer between tests, which can shift the reading several kilograms.
The wording of this protocol is Evolution’s own draft rather than supplied copy, and is marked as such inside the product too.
The evidence
What it actually shows
The reference distribution is Dodds and colleagues, who pooled twelve British studies covering 49,964 people aged 4 to 90 and published centiles across the whole range. Grip peaks at around 32 in both sexes — roughly 52 kg for men and 31 kg for women — and declines from there.
Grip is scored on the dominant hand, best of the recorded attempts. It earns its place in the Index because it tracks strength you cannot easily measure at home and because it moves early: it falls before the things people notice falling.
In the Evolution Index it carries thirty per cent of the strength domain, alongside fat-free mass index, lower-body power and the dead hang.
The number depends on the instrument and the position. Handheld dynamometers differ between models, and a reading taken seated with the elbow at ninety degrees is not the same measurement as one taken standing. Two sources cannot be mixed, and a reading from a different device is a different test.
Dodds is a reference distribution, not an outcome study. It tells you where you stand against British adults your age and sex; it does not by itself predict anything about you.
The thresholds the Index scores grip against are Evolution's own, informed by that reference rather than lifted from it. They are stated as thresholds, not presented as a published percentile table.
Dodds RM and colleagues. PLOS ONE 2014;9(12):e113637. 49,964 participants across twelve British studies, centiles for ages 4–90.
The next step
One test is one test.
This measures one thing. The Evolution Index measures nine, across the three domains that decide how long you stay useful, and reports your weakest rather than your average — a strong heart does not buy you out of a floor you cannot get up from.
Every score is published with the error around it, because a change smaller than the measurement error is not a change.