Does training of some major muscles groups enhance overall muscle growth?

Question

There is a popular (e.g. link 1, link 2) theory, that is, if you train big muscle groups (e.g. legs, chest), it will increase the overall growth of muscles all over the body; the trained muscle will release signals (what are they?) into the blood stream and in turn, triggers the release of muscle growth/repair hormones (insulin-like growth factor?) which have effects on any (skeleton) muscle cells.

Is this story true? Will the muscle growth/repair hormones also enhance the smooth muscle or cardiac muscle?

Answer 1

Performing compound exercise movements have been shown to trigger the pituitary gland to release Human Growth Hormone. HGH does not discriminate against the muscle cells it targets. In a paper titled Growth Hormone and the Heart, it was shown that

GH exerts direct effects on myocardial growth and function. Evidence from laboratory models shows that GH (or IGF-I) induces mRNA expression for specific contractile proteins and myocyte hypertrophy.

And,

The data also support a role of GH in the maintenance of a normal cardiac structure and performance.

In fact, cardiovascular researchers have also looked to HGH in recent years as a potential benefit for those with congestive heart failure (CHF).

In summary, increasingly, scientific data exists suggesting that bio-identical hormone replacement might be crucial in maintaining adequate heart health and improving the lives of people already suffering from cardiovascular disease.