[stared]

Without a control group, correlation is not causation. So the opening sentence is misleading, exaggerated, or maybe even plain false:

> Adults should aim to do between 560 and 610 minutes a week of moderate to vigorous physical activity to achieve a substantial reduction in the risk of heart attacks and stroke, suggest the findings of an observational study published online in the British Journal of Sports Medicine.

It is highly likely that healthier people exercise more (and the bedridden exercise way less). Also, who exercise more: people who care about their health in general, who don't overwork themselves, who have disposable time and income.

For example, an older person's walking pace is strongly correlated with their remaining life years. If we force these people to walk faster, they won't outrun death - we would very likely just increase their mortality.