Ever taken prolonged time off training, or been injured and laid-up for a while? Strength tends to drop quite rapidly, but you’ll notice that eventually, continued inactivity leads to muscle loss. If you’ve gotten back onto the training wagon you may have also noticed that your muscle mass returns to its previous size a lot quicker than it took to build it in the first place. This is referred to as “muscle memory” and some researchers from the University of Oslo .
is quite a generic phrase and does not necessarily focus on just the return of previous muscle mass. It also includes the memory of muscles (and the nervous system) for task performance. No doubt you’ll have heard of the phrase “it’s like riding a bike”, which implies that once you’ve learned how to ride a bike it’s a skill you’ll have for the rest of your life. This is muscle memory.
But what about the rapid return of muscle size? Through the years I have read several theories for this, including one put forth that it is down to the stretching of the muscle fascia allowing for growth (apparently once this fascia is stretched once it doesn’t return to its original capacity, thus allowing for faster growth next time round). But the Norwegian scientists have given a different theory on a cellular level.
Resistance training leads to an increase in muscle fiber size and thus bigger muscles. The researchers also found that the number of nuclei increases to support the growth processes necessary in muscle cells (the nucleus directs protein synthesis), which are huge in comparison to other cells in the body. When training is ceased and the fibers begin to atrophy, these extra nuclei are not destroyed, but appear to remain intact. This means that when the person resumes resistance training, they have more of the machinery in the muscle fibers for making them bigger.
The full research paper is available free via open accessfor anyone wanting to read the full details.
Source: Bruusgaard JC, Johansen IB, Egner IM, Rana ZA, Gundersen K. Myonuclei acquired by overload exercise precede hypertrophy and are not lost on detraining. Proc Natl Acad Sci U S A. 2010 Aug 16.