What is the minimum amount of exercise that actually improves health?

Less than most people assume, and the biggest health returns come from moving from zero to something rather than from good to optimal. The commonly cited target is 150 minutes of moderate activity a week plus two strength sessions, but meaningful mortality benefit appears well below that — even 60 to 90 minutes a week shows clear effect in large studies. Strength work twice a week matters independently, particularly after 40, for muscle mass and bone. If the full target feels unreachable, the useful message is that half of it is not half as good, it is most of the benefit.