Does anyone know if the tiredness is reset at the end of the season?
Thanks

Does it was mention somewhere (FAQ/Help/Admin)?
(I've seen the same answer on rookie forum, however no mention about the source of this information)

Going forward, I see the only chances of lowering/increasing fitness only training. This mean that if you train with higher intensity one week, you need to train with corresponding lower intensity next week in order to be OK. Or train average always.

So the following question comes to my mind : what is the usage of high/low level of training? As on long run number of high intensity weeks will be offset by the number of low intensity weeks, this results in the same result as a flat average on long run?
Wouldn't be necessary an extra option to increase back your fitness (a medical center or stuff like this) ?

Yes this in theory...
But you can be terribly lucky or terribly unlucky...
Statistically it 4-5 average for a high and 7-8 average for a maximum.