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Muscle Memory: Scientists May Have Unwittingly Uncovered Its Mystery
By Byran Haycock, MS
Anyone who has lifted weights, on and off, for several years is familiar with the concept of "muscle memory". Muscle memory in this context refers to the observation that when a person begins lifting weights after a prolonged lay off, it is much easier to return to their previous levels of size and strength than it was to get there the first time around. Even when significant atrophy (muscle shrinking) has taken place during the layoff, previously hypertrophied muscle returns to its previous size more quickly than usual.
A recent study looking at fiber type conversions during muscle hypertrophy may have uncovered a possible mechanism for this phenomenon. For those of you not crazy about scientific lingo bear with me. Towards the end you will see what I’m getting at with this study. In this study the distribution of myosin heavy chain (MHC) isoforms, fiber type composition, and fiber size of the vastus lateralis muscle were analyzed in a group of adult sedentary men before and after 3 months of resistance training and then again, after 3 months of detraining. Following the period of resistance training, MHC IIX content decreased from just over 9% to 2.0%, with a corresponding increase in MHC IIA (42% to 49%). Following detraining the amount of MHC IIX reached values that were higher than before and during resistance training, over 17%! As expected, significant hypertrophy was observed for the type II fibers after resistance training, and even remained larger than baseline after 3 months of detraining.
By Byran Haycock, MS
Anyone who has lifted weights, on and off, for several years is familiar with the concept of "muscle memory". Muscle memory in this context refers to the observation that when a person begins lifting weights after a prolonged lay off, it is much easier to return to their previous levels of size and strength than it was to get there the first time around. Even when significant atrophy (muscle shrinking) has taken place during the layoff, previously hypertrophied muscle returns to its previous size more quickly than usual.
A recent study looking at fiber type conversions during muscle hypertrophy may have uncovered a possible mechanism for this phenomenon. For those of you not crazy about scientific lingo bear with me. Towards the end you will see what I’m getting at with this study. In this study the distribution of myosin heavy chain (MHC) isoforms, fiber type composition, and fiber size of the vastus lateralis muscle were analyzed in a group of adult sedentary men before and after 3 months of resistance training and then again, after 3 months of detraining. Following the period of resistance training, MHC IIX content decreased from just over 9% to 2.0%, with a corresponding increase in MHC IIA (42% to 49%). Following detraining the amount of MHC IIX reached values that were higher than before and during resistance training, over 17%! As expected, significant hypertrophy was observed for the type II fibers after resistance training, and even remained larger than baseline after 3 months of detraining.
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