Is muscle plasticity the same thing as when muscles regenerate from wear and tear?

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I am writing a fantasy sci-fi, that is almost the same as our reality, the only difference being humans in this world are capable of using drugs (serums in their world) to improve their bodies' capabilities since ancient times (pre-agricultural).

Like making the body more efficient in order to survive extreme environments for weeks or months without the need for crucial gear, enhancing the body's immune system to cure diseases and toxins in record time, heightening alertness, keeping the body in peak physical condition for vast periods and, most importantly, cutting training time by raising neuro and muscle plasticity.

Even with all those miracle drugs they never were capable of creating serums capable of improving the body's regeneration. Until someone discovered something and the rest is history.

I want to use the regenerative serums, as a plot device for an army super training regime program. Fundamentally, they train hard every day wihout stopping, if an average human did this, he would tear a muscle or break a bone sooner or later. Using the regenerative serums, they heal overnight. Creating super dense muscles and bones after repeating the process countless times, forget swimming, even floating is impossible, any large bodies of water for that matter, their very own kryptonite, maybe I will use it in the story.

My Question

Is muscle plasticity the same as muscle regeneration from wear?

If it is can I change muscle plasticity for muscle memory?

I want to differentiate the serums capable of accelerating physical and mental training from the regenerative serum's used to create the super training regime. The reason is to have more diversity and complexity in my world, having soldier highly skilled for special missions and super grunts for the heat of battle.

Answer 1

Muscle plasticity is not the same thing as regeneration.

Muscle plasticity is defined as the ability of a given muscle to alter its structural and functional properties in accordance with the environmental conditions imposed on it....

From birth until death, skeletal muscle is in a constant state of remodeling in order to adjust to changes in load, activity, or innervation. This unique plasticity allows muscle to alter its structural and functional properties in accordance with its imposed environmental conditions. This is widely recognized in sports, where muscle changes imposed by training in athletes leads to obvious phenotypic modifications that optimize the specific performance of the muscle. The number of muscular contractions (activity) and the degree of loading appear to be the dominant stimuli for training-imposed muscle changes. For example, body builders perform low frequency, high load contractions that result in muscle growth (i.e., hypertrophy) and an increase in force-generating capacity. On the other hand, marathon runners perform high frequency, low load contractions that are not associated with hypertrophy, but cause muscle fibers to assume a more fatigue-resistant phenotype. Although genetic pre-disposition is also important, these adaptations, substantially contribute to the different physical attributes of body builders and marathon runners. (ref)

Exercise does break down muscle fibers. When you sleep, your pituitary releases growth hormone which helps in rebuilding the muscle to be stronger. The exercise doesn't build the muscle directly, though of course it's the catalyst.

After you workout, your body repairs or replaces damaged muscle fibers through a cellular process where it fuses muscle fibers together to form new muscle protein strands or myofibrils. These repaired myofibrils increase in thickness and number to create muscle hypertrophy (growth). Muscle growth occurs whenever the rate of muscle protein synthesis is greater than the rate of muscle protein breakdown. This adaption, however, does not happen while you actually lift the weights. Instead, it occurs while you rest. (ref)

While you might call this normal nightly rebuilding (something that happens every night, regardless of activity, if you have enough growth hormone) regeneration, it's not the magic regenerative serum you reference in healing injury. I'll note that you refer to "wear and tear" but your examples are about injury.

When you tear a muscle, you literally tear it. I've had hard workouts that have left me sore for a couple of days. But one day (literally in a fraction of a second) I tore my calf muscle. It wasn't even that bad a tear (level 2 out of 4), but I was on crutches for 2 months.

When you tear a muscle or break a bone, you can not put weight on it while it's healing. And healing takes time. It was 2 weeks before I was allowed to put any weight on my leg and another 2 weeks before I could gently walk with most of my weight held up by the crutches. Broken bones take longer. (Where the break or rip is will change the timing, but it doesn't change the reality of healing.)

If you want to use magic for this overnight healing, sure, go ahead. Or if you want to call it science fiction and handwave how it works, okay, it's your story. But you're asking for science-based and the science simply isn't there. Might it be in the future? Perhaps to some degree. But only in that it will speed healing, not make it unnecessary.

When your soldiers train while they are injured (this is implied by your wording, even if it's only for a couple of hours, it counts), they are compounding the injury many times over. Training hard again the next day would compound the original injury as well.

My frame challenge to you is in how you incorporate the idea of outright injury into this program. That's not how you make soldiers stronger faster (or ever). Perhaps you didn't mean to put it that way, but I can only answer the question in front of me, not the one that's actually in your head.