Inducing the expression of MGF
MGF is naturally produced when muscles are stretched during exercise. MGF activates stem cells already present in the tissue and, once activated, progenitor cells begin to divide and to create new cells. In addition to intensive exercise, muscles need to be stimulated by GH in order to release MGF.
The correlation between stretching and MGF can be traced back to the 1980s when John Parillo introduced fascia or extreme stretching while muscles are still pumped from a gym session. Parillo’s idea was that fascia should be more elastic so that muscles have more room to grow. He believed the benefits of extreme stretching to be two-fold: Expanding the fascia and inducing the expression of MGF. When muscles are stretched during exercise, they start pumping out their own supply of MGF which activates stem cells already present in the muscles. Once activated, these progenitor cells begin to divide, creating additional muscle fibres and increasing the size and strength of the muscle.
Dante Trudel, a.k.a. Dogg Crapp, (from his username on an internet forum board) also advocated extreme stretching as part of his training system.
Scientists have found the resting levels of MGF in muscle to be 100-fold lower than muscle-liver mediated IGF-1. MGF levels also increase in young men after exercising as compared to older men. This generally occurs because, as we grow older, hormonal and physical activity levels decrease and muscle wasting occurs.
In one study, men of different age groups (young and old) performed leg extensions after which muscle biopsies were taken in the post-exercise period and examined for MGF gene responses. It was found that MGF levels significantly increased in younger male subjects in response to the bout of resistance training and there was no change in the older participants. It was also noted that the muscle-liver type IGF-1 remained the same in both groups. According to the study, some young subjects increased their MGF levels with as much as 864 percent after training.
Similar studies in rodents have shown that older rats have a blunted MGF response to mechanical damage of muscle, which only reinforced the fact that MGF responses are attenuated as humans age. It was also determined that basal levels of MGF in muscle were directly related to the size of the muscles.