I would say I am completely lost how hard physical work can cause a new or enlarged muscle to be established in
. People who do high intensity work, long distance runners
and the like, do develop stronger than normal cardiovascular systems, including some enlargement and strengthening of the heart, I believe. This may be true of intense weight lifting too, i.e., hard and heavy lifting associated with work. None of this has in to my knowledge anything to do with heart problems.