Very important to use right terminology, I agree. Therefore:
Altered gene expression (in effect to certain training loads) results in variations (increase / decrease) in the amount of specific proteins in muscle (an adaptive change).
The capacity for adaptive change of the skeletal muscle is termed myoplasticity.
Please note that its an adaptive phenomena.
The definitions you use are wrong. Faster of slower changes in muscle are both adaptations.
Capacity for such adaptations is plasticity.
Research showing transition from type I to type II is not conclusive yet. It appears that
voluntary effort (hence usual training loads)does not cause such shifts.
However, cross-innervation and cross-transplantation experiments , and direct stimulation with various frequencies show that its possible to alter MHC expression.
EMS is a very good candidate for this.