As an individual, your social isolation and your physical activity are both independently under your control. So it's useful to know their relative impacts on m

As an individual, your social isolation and your physical activity are both independently under your control. So it's useful to know their relative impacts on mental health. Suppose it turned out that, when controlling for physical activity, isolation had no effect on health. Then, in the next pandemic, you should mostly focus on exercise. Or if isolation is more important, then you should focus on that.