It is often claimed that muscle damage is a cause for muscle strength and hypertrophy, but if this is the case, then if i cause some micro-tears to a muscle using, say, some tiny needles, would that cause muscle hypertrophy? How is this type of muscle damage different from the one caused by training?
So I'm going to attempt explain this simply as possible:
Long chains of proteins called Actin and Myosin are contained within your muscles. Resistance training stimulates the growth of new chains of these contractile proteins.
This leads to increased strength and size of the contractile unit of muscle. So the current cross-bridges you have are now more efficient and in addition you've increased the number of force producing cross bridges.
Induced muscle micro-trauma by methods (such as puncturing it with a needle) does not have any effect on the function or development of these force producing proteins.
Why the muscle micro-tears occur determine the resulting physiological and muscle adaptions.