Say I run 5 times a week, 2 hard sessions and 3 easy sessions are usually considered better than 5 sessions at the same level.
What would be the best approach to estimate how optimal my effort is from such a viewpoint? Assume I can capture all appropriate data.
The example is very simplified of course. Especially one should see it in context over longer periods.
ideally I would like some kind of precise mathematical formula, but that does probably not exist.
Other answers could be
Use the knowledge and intuition of a personal trainer.
Develop my own intuition by reading this forum
An example of what I would like to know, is the relative benefit, on a particular day, of say biking to the office or gym, or to know how much I should push myself in what I do. (The complete answer is outside the scope of this question.)
The real world for me is quite complex - different activities etc. I don't have any particular goals, just to gradually become fitter and used to higher loads.