"He has the muscle memory to make a quick come-back."
|cross section of skeletal muscle|
And it's true! But how do muscles remember? If you ask them to do anything more than shorten, they'll just sit there all jacked, with a blank stare on their face. Although it sounds 14% less cool, muscle memory is technically motor memory. The key player in motor memory is, of course, the brain, which can't do a darn thing for itself but is great at shooting orders.
What exactly does the brain "remember?"
1. Desire. First of all, trained people often want to regain their physical abilities. They have tasted and seen what life is like as a solid force of a person and usually have great motivation to avoid the alternative.
2. Previously trained brains have learned how to suffer. They are willing to put up with the misery, even embrace it, because they realize the triple pay off. They know that "no pain, no gain" is a half truth, and can easily discriminate between physical damage and beneficial discomfort.
3. The brain remembers the circuitry of skilled movement. Riding a bike is, well, like riding a bike. The neurological motor plans of lifting, running, jumping, throwing, etc, last much longer than the actual physical ability to perform them. Deconditioned athletes reap the rewards of having worked through thousands or tens of thousands of well executed repetitions in the past. The body may be soft and weak, but the brain hasn't forgotten.
4. On the more technical side, through consistent and regular training, the brain learns how to signal the muscles more efficiently. Through rate coding (bundling nerve signals in the most efficient manner), motor unit synchronization (getting various muscles and parts of muscles on the same page and working together), and reciprocal inhibition (getting opposing muscles to relax and even contribute through improved stabilization), the brain literally knows how to get more out of the body.
5. When a muscle is exercised, nuclei are added, and they're not lost when muscles atrophy. Some scientists think this is an additional reason why previously trained people do bounce back more rapidly than untrained folks.
In summary, muscle memory is a brain skill, earned through years in the training trenches, that's not easily erased by a little time off. Go out and get you some!
Bonus: Muscle memory can be "built" quicker and to a greater extent by getting powerful and efficient in a few basic exercises rather than switching your program every other week. Muscle confusion is like, so 2007.