First question is about innervation.

Is there only one nerve per fibre (sarcomere series)?

If so any resistance training ought to equilabrate stress along the sarcomere series, thus it ought to be impossible to train one end of the series more than the other, unlike what is documented here.

Preprint Regional Hypertrophy with Resistance Training -Does Muscle L...

Unless there is a degree of reflexive decentralized autonomy within individual sarcomeres.