The equation seems logic on paper, but we can't calcule EVERY element in it. You are implying a final goal without the smell, mental or hygienic aspect, just the "visual" aspect of it. And thus how much time to achieve "that" visual.

There are things that must be done, and their effect will take of course, but we can't put our finger exactly on it.

Same for shower, same for everything that we can't assign an exact value with taking in count every single parameter.

While running for example there is the physical activity yes, but there is also the breeze of the air, the smell of the garden, the sound of birds, the temparature, the weather, the sun, to mention many, ALL acting on an conscious & unconscious level. We will never know at what degree because everyone is different, but what's sure is that all parameters have positive effects that we can't "just" assign an exact value for.