Field
Measurement
The numbers used to describe ageing, and how much each one is worth.
- Blue ZonesmixedRegions reported to have exceptional longevity, and the data-quality problem underneath them.
- Chair-stand testgoodFive chair rises and a stopwatch. Legs as a longevity readout.
- FrailtygoodA measurable loss of physiological reserve. Not a synonym for age.
- Gait speedgoodThe cheapest survival predictor in geriatrics. Walk more, but do not train the test.
- Grip strengthgoodA five-second test that predicts a lot. Train the body, not the grip.
- Grip strength and mortality: 38 cohorts, 1.9 million people, one number to carrygoodA hand that squeezes a dynamometer hard is one of the few measures that predicts mortality as well as blood pressure does. Nobody has run the trial that would explain it.
- Lifespan vs. healthspangoodYears alive versus years in good health. The gap between them is the thing worth shrinking.
- Telomere length and mortality: what the cohorts showgoodShort telomeres track higher mortality in almost every cohort that has measured them, and the effect shrinks in the oldest old. Nobody has shown that changing them changes anything.
- The ten-second balance testgoodTen seconds on one leg, no equipment — and a surprisingly strong signal about survival.
- Training load and fatigue: what the studies could and could not measurethinThere is no blood test for overtraining. The best-reviewed candidate is a battery of measurements, and the review that mapped it found 39 studies out of 5,561.
- VO2 max and cardiorespiratory fitnessgoodAerobic capacity. Strongly predictive, genuinely trainable, rarely measured.