Blood pressure

Blood pressure is measured in millimetres of mercury and written as two numbers: systolic, the peak during a heartbeat, over diastolic, the trough between beats. Normal is generally taken as under about 120 over 80, with hypertension defined by thresholds that vary a little between guidelines.

It matters because high blood pressure is the single largest modifiable risk factor for stroke and a major one for heart attack, kidney disease and dementia — and it is symptomless until it causes damage, which is why it is worth measuring rather than guessing at.

In practice it responds well to exercise: regular aerobic training typically lowers systolic pressure by several millimetres of mercury, and isometric training has surprisingly strong evidence for the same. Reducing sodium, losing excess weight, moderating alcohol and sleeping properly all contribute.