This article goes in depth about the biological mechanism in which muscle fibers respond to some sort of strength training or steroid use. Researchers have found that having a previous history of anabolic steroid use has lead to a greater increase in muscle mass after periods of inactivity. They contribute this to the idea of "muscle memory", essentially giving cells a head start on a process they are already familiar with. An explanation that they have proposed is based on the fact that muscle fibers have multiple nuclei, these myonuclei increase in number with the enlargement of muscle mass. When going through periods of inactivity, muscle mass decreases, but the number of myonuclei remain the same. The increased number of myonuclei contributes to the cells muscle memory when undergoing subsequent muscle hypertrophy.
These experiments were run by implanting a testosterone pellet in the skin of the neck of female mice. 14 days after implantation, the number of myonuclei increased by 66%, increasing the muscle fiber cross sectional area by a whooping 77%. The mice strictly subjected to vigorous exercise only saw an increase in myonuclei by 51% and a 48% rise in cross sectional area. Less than a week after removal of the testosterone pellet, the level of testosterone in the blood was nearly undetectable. 3 weeks after removal, the muscles were analyzed. The muscles showed a 41% retention rate of the myonuclei. During subsequent overload exercise, the previously exposed testosterone group showed a 27% greater increase in muscle mass in comparison to the control group.
This article is appealing to me because I enjoy learning about health and fitness related topics. I also want to encourage people to get out there and be active! These are your prime years, might as well take advantage of that. Hope anyone who reads this thought it was as interesting as I did.
Here's the link to the article:
http://jp.physoc.org/content/early/2013/10/28/jphysiol.2013.264457.full.pdf+html
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