Holding a single-leg balance for 10 seconds is a simple, well-documented test: failing it is associated with a higher risk of death in people aged 51-75, and the test improves risk prediction beyond age and standard clinical factors.

noli's read

A study published in the British Journal of Sports Medicine (2022, n=1,702, ages 51-75) found that inability to hold a 10-second one-legged stance was associated with an 84% higher all-cause mortality risk over 7 years of follow-up, even after adjusting for age, sex, BMI, and comorbidities. A companion Japanese cohort (Aizu, LOHAS) confirms that a shorter single-leg stance time is associated with loss of independence or death, including in people whose better-performing leg was within normal range. These are observational associations (balance likely reflects underlying frailty or physiological resilience rather than directly causing death), and the test alone doesn't replace a health checkup. But it's a simple, free, well-validated marker, and balance is trainable (yoga, tai chi, resistance work) according to existing controlled trials — Bryan Johnson's framing here is faithful to what the research shows.

the sources

No named source held this one up — that absence is part of the verdict.