When new muscle fibers are formed through hypertrophy, how long does it take for motor neurons to connect to the new muscle cells in order to be able to control them?
After taking a break from working out, I noticed that my strength has actually increased and I wondered that maybe although the new muscle cells were already built back when I was working out, they weren't yet connected to the nervous system and so I couldn't "access" this strength.
The question is quite interesting. what is the time required to newly establish a neural connection to newly formed muscles? Unfortunately the answer is NO.
No new muscles are formed by hypertrophy.
This is because you are referring to hypertrophy, not hyperplasia, which are essentially different. Hypertrophy is increase in the muscular fibers due to increase in mitochondria, myofibrils and other cell organelles. The size and volume of cell increases but the number of muscular cells remains same, hence there is no change in the nerve connections. The nerve connections essentially remain same. When you do strength training, the proteins i.e. actin and myosin undergo wear and tear. This damaged is repaired by synthesis of these proteins which is results in muscular hypertrophy.
Hyperplasia is increase in number of cells. Which brings us to next question, do muscle cells divide? The answer is YES, but it is largely restricted. These cells are termed as satellite cells.
So new neural connections are established probably only if new muscle fibers are formed.