I am an unfortunate female soul that ended up in a male body. How did it happen? It can be magic or some unfathomable technology indistinguishable from magic. I will investigate, but right now I need to ensure my survival in this new world (I was too overwhelmed with my circumstances before and forgot to mention it, but I am no longer on modern Earth). I need to learn martial arts ASAP if I want to keep my little life.

The original me (the female soul in a female body) was an average woman living in a developed country and working an ordinary desk job (my existence was the very definition of boring). I did not have any major health problems but I was not exceptionally fit. My experience with physical exercises in adulthood was limited to irregular ballroom dance classes and occasional dance parties. As a child, I trained as a swimmer and a ballet dancer (I blame my parents who could never agree on anything!) and thus mentally prepared for the pain and suffering of martial arts training (or so I tell myself). I also cherish my life and am willing to put time and effort into gaining skills necessary for survival.

The original owner of my new body (the male one, in this new world) practised martial arts: breathing exercises, swordsmanship, and unarmed combat. He was not particularly talented or motivated, so his achievements were nothing to brag about. I think that he should have some muscle memory given that he was training for many years (apparently they usually start martial arts training at the age of 6-7 and my body is 17) and was praised for his proficiency in basic forms.

Considering that muscle memory allows the performance of learnt movements without much conscious effort, what role will a pre-existing muscle memory play in the acquisition of martial skills? Will I have the same (or close to the same) level of proficiency as the previous soul or will I be forced to start from the very beginning? Also, if my new body had bad martial art habits how hard would it be to fix them (as someone who went through the pain of correcting a poor piano playing technique I am quite interested in this aspect)?

I am not looking for the exact numbers (it is not possible). I am trying to set clear expectations and gather some understanding of the principles behind muscle memory (how independent it is from consciousness) in order to come up with a realistic training regime. I would appreciate it if the answers were based on science (links to the academic papers are more than welcome).

If it is important, I am thinking about switching to a folding fan and a whip as my preferred weapons in the future.

About soul and body interactions:

  • this is not a forced possession where my soul acts as a puppeteer and has to control every single aspect and movement of the body;
  • the control is 'natural' and all automated body functions work as expected;
  • my soul has a mental image of the body that is informed by my previous body and has to be adjusted for my current body: This causes cognitive dissonance and some problems with coordination and non-automatic actions (the latter should disappear after I fully adjust, the adjustment period is estimated to be no more than a year, 3-4 months for most everyday activities);
  • my mental state is affected by the body's physiology: Mostly my moods and emotional responses (this will not be a problem at all after a year or two since I found a solution for my emotions);
  • if you feel uncomfortable with the word 'soul' you can substitute it with 'consciousness', they are equivalent within the scope of this question.
  • if you have difficulties accepting the premise, you can think about it in terms of explicit memory replacement (accomplished by the mighty and mysterious handwavium): Explicit memory of the male was replaced with my explicit memory leaving the majority of the nervous system intact.

If you need clarifications or additional details, please, ask in the comments.

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    $\begingroup$ muscle memory is not stored in the muscle but in the brain, specifically the cerebellum. if your clarkian magic is over righting the brain it is overwriting muscle memory. $\endgroup$
    – John
    May 24, 2021 at 14:01
  • $\begingroup$ It isn't important for your question, but fans are an impromptu weapon and not a primary weapon. Consider the legends of self-defense with fans as similar to the legends of Robin Hood splitting one arrow with another arrow - they're legends because they're so damn improbable. Whips work a bit against unarmoured opponents, but not at all against armour. There's a reason you don't find them on the battlefield, or even in duels. $\endgroup$
    – Graham
    May 24, 2021 at 16:13
  • $\begingroup$ @Graham Fans are historically accurate weapons. See tessen. $\endgroup$
    – Otkin
    May 24, 2021 at 19:10
  • $\begingroup$ @John If it makes it easier for you to imagine my premise try to think about it as a full memory replacement without affecting the body and nervous system. Yes, this requires some handwavium, but it is a fantasy setting. $\endgroup$
    – Otkin
    May 24, 2021 at 19:23
  • $\begingroup$ @Otkin Benches are historically accurate weapons too - there's a form using them. It doesn't mean that anyone would choose to use them as a primary weapon against a sword or spear, except as a big "f*** you" to humiliate someone you're that much better than. $\endgroup$
    – Graham
    May 24, 2021 at 20:46

6 Answers 6


It will allow you to... Either skip the "getting stronger muscles" part or require little to no training

Truth is, muscle memory as you're saying it isn't really quite how it works. The muscles themselves don't remember how to automatically perform a task, what they do remember is how to "grow back" in a way if you exercise, which is why previously muscular people who go back to the gym after a long period of inactivity usually have faster muscle growth than in the first time, although we're not 100% sure how exactly.

The muscle memory you're thinking of, however, would be closer to neural muscle memory, which rather than the muscles themselves learning how to perform a repetitive task, it's actually an association between your muscles and brain, particularly the unconscious part, like some martial artists would say. What's actually happening is, through lots of repetitive movements, you're creating what one could call a "memory map" , which is essentially your brain learning better and better how to use certain groups of muscle to perform a certain task, and this applies not only to martial arts, but even to other simpler activities like getting a hold of a glass or cup (it's not that the muscles themselves undergo no changes whatsoever, they do, but it still takes the brain to work. A dead karate master won't really give a skillful chop if you just electrocute the muscle groups they'd use unless you do it just like the brain would during the performance of said chop, and no, it's not muscle memory that allows dead fish to swim upstream).

Since these memory maps are only really usable if you have the person's brain (or at least brain structure, I assume), we have 2 potential outcomes:

1-your memories aren't completely magic and this soul transfer altered the previous owner's synapses so that his brain patterns were essentially identical to yours, essentially replacing all of the information stored in his brain with the information stored in yours: you probably should have no muscle memory whatsoever, since the unconscious associations are gone. You might still have access to the previous owner's strength, and even if you don't, his muscles will still develop faster than if he didn't practice any physical activities and was developing his muscles for the first time, so you'll still progress faster in the muscle building department at the very least. I sadly can't affirm any of these (except the faster muscle building part) with absolute certainty since I'm no neurologist, I don't know any karate master whose soul was replaced with that of an untrained accountant whose experiences I could ask about and the brain is essentially the most complex organic computer that exists and not even the greatest scientists of the field truly understand every bit of how it works.

2-your memories are completely magic and this soul transfer didn't alter the previous owner's synapses so that his brain patterns were essentially identical to yours: you're already a martial artist. All of his memory maps are still there, and chances are that since you have access to his brain, you can also access his memories on how to train and perform the moves and exercises he knew. You won't need to train to reach his level and it's mostly assured that your efforts from then on will be solely to improve on the foundations that have already been established by the body's previous controller. Good luck being a consciousness having to deal with 2 sets of completely different memories of life though, you might end up trying to harmonize both and become someone that's both yet neither.

also if the thing in your pelvis swells up, don't try to stop it, it'll become self-sustaining if you do so.



Muscle control happens on several levels, but can be condensed to brain, spine and the rest. These control all of it. Now it just matters what happens to these structures the moment a different soul gets in.

On the surface it seems simple. A soul is not a brain, spine or other, so all structures are in tact and Identical. No differences means no loss in muscle memory. But no differences would also mean the soul transfer wouldn't really matter. The memories, thoughts and everything would be identical. The female soul would be the man, 1 on 1.

Problem starts with the female knowing she used to be female. Remembering things is, among other things, a way the brain is structured. How can she remember being a female without the correct structures? This implies change. It is them important to know how far that change goes. Memory is not only in the limbic system it's an intricate effort in the whole brain. A movement, feeling, visual stimuli or other all are triggered in certain ways, each having their own depth of memory on many ways.

There are very many problems, but it might be 'easiest' to solve them. The most personal memories and recognition are somehow transferred to the brain, replacing all or nearly all of the previous occupant. This will likely trigger deja vu or other similar thoughts or feelings which are difficult to determine who is the original source in many less determined memory cases. But what you will have is the right muscle memory and recognition when to use them. It might be seamless, but there is a chance some of the martial arts need to be done to unlock all of it very quickly, thanks to associative memory.


Martial arts instructor here. The school I went to focuses a lot on footwork; and for weapon usage, it's much the same whether you are wielding a staff, a dadao, a spear or if you are fighting bare handed.

I had already spent years training with all kinds of swords before I even held a spear for the first time (not related to any skill progression, I simply didn't have a spear before). I went to some classes for instructors only for that weapon. We trained footwork, but since we all had a lot of practice, that part went smooth and we went through practically automatically.

I can tell you that when giving classes, I had to do a lot of stance and foot work with new students; as they progressed, I could focus more on teaching the handling of new weapons and less on teaching stance and changing directions.

I figure that if your character would compound on techniques. The basic ones, which are the foundation for the advanced ones, would not need to be completely relearned. They might have to review some aspects of the basics to learn more advanced stuff, but that might not be a big deal.

  • $\begingroup$ How hard is it to correct poor habits? Assuming that after learning proper basics the character was taught improperly (on purpose). $\endgroup$
    – Otkin
    May 24, 2021 at 19:16
  • $\begingroup$ @otkin every case is different, even for the same person. I used to blink when parrying and it took me a afternoon to fix that. But in nearly a decade of practice I could never once land a perfect kick with my left leg. $\endgroup$ May 24, 2021 at 20:39
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    $\begingroup$ Is my understanding correct that I have full creative freedom when it comes to fixing bad habits? In other words, whether it takes 1 year or 10 you, as a martial arts instructor, will find it sufficiently realistic. [I am working on a fantasy project but I strive for greater realism] $\endgroup$
    – Otkin
    May 24, 2021 at 21:09
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    $\begingroup$ @otkin yes, you are correct. I also recommend reading the Book of Five Rings, by Musashi. He is largely considered the greatest swordsman to have ever lived and he spends a portion of the book criticizing what he saw as bad habits displayed by fencers of renowned schools and who had a lifetime of practice. $\endgroup$ May 24, 2021 at 23:20
  • $\begingroup$ Thank you for the reference! I will definitely read it. An opinion of a master swordsman would be the most beneficial for my writing. $\endgroup$
    – Otkin
    May 25, 2021 at 0:47

I'm not neuroscientist, but... The nervous system and body have developed from conception together and are all tuned together as they have grown and changed over time. Muscle memory as commonly talked about mostly isn't actually in the muscles, it is in the brain and wider nervous system. Some is in the muscles in that both the muscles and nerves are tuned simultaneously as you train: as you learn new movements the muscles develop to support them, and as the muscles develop the nervous system is tuned for the changes in strength and flexibility.

This coordinated tuning isn't just for conscious movements though. All the little adjustments you constantly make to keep balance while just standing, never mind taking part in the complex movements for martial arts. If you somehow lift one nervous system wholesale into another body, it won't know how to effectively & efficiently manage those adjustments in the new body with its diffing muscle strengths / centre of gravity / etc. It'll take a while to even stand well.

Also autonomic functions, even though they can run on autopilot so keep going when someone is in a complete coma, are not entirely decoupled from the rest of the body. That lifted & shifted nervous system won't immediately be able to efficiently manage that new body's breathing and such. The new "soul" would need time to adjust to that before even trying to stand.

What could this mean for a mind-swap? This implies that for the swap to be successful without months of recuperative retraining, it must be partial. Transfer the memories and conscious drives but leave as much of the core body management in-place and somehow knit the two together. It may not be possible scientifically to identify and separate these functions within the source and host brains, so you are probably looking at a magical or hand-wavey solution narratively, but the fact that it would be necessary to perform a partial transfer like this could be the justification for "muscle memory" from the previous occupant still being available to the new controlling mind.

  • $\begingroup$ While I agree with your assessment so far, this doesn't answer the question as asked. If that muscle memory is still available, how useful would that be in mastering a martial art? $\endgroup$ May 24, 2021 at 13:27
  • $\begingroup$ I also agree with your words, but I would appreciate it if you could offer an answer to my question. You can assume that we are talking about partial mind-swap as described in the last paragraph. $\endgroup$
    – Otkin
    May 24, 2021 at 19:32

Literally however you want it to.

Since you're talking about a completely fictional phenomenon (one consciousness taking over the body of another person), any skills or knowledge you want the person to gain from the body they are inhabiting is entirely up to you, the writer. You define how the rules of your world work, so if you want the person to be able to inherit the skills of the body they are inhabiting, then just write it that way. You could even have the person retain some of those skills, so that when she returns back to her original body, she can still perform martial arts to some degree. It's equally possible that the man whose body she is inhabiting will also retain something from the experience once he's back in control of his body. Do you want that to be a factor? Then just write it that way. If not, then don't, your choice. There's no real-world analog to this situation that you have to be beholden to, so you're free to write the rules however you feel like. Just be internally consistent. If it works one way this time, it should work the same way next time if it happens again, unless the change in the rules is part of the story.


Benefits of former training:
As with most training, you should stop worrying and start training. Get behind what kind of martial art your body did and start a beginners class. Entrench yourself in training and rise fastly through the ranks. If this kind of training is not available, do calisthenics to keep fit and look for similar style of art.

If meditation is part of what your body used to train, use it to reconnect your current mind to your body.

The advantage of starting with a beginners class is you learn good form, muscle memory should help you get through initial stages much faster then the average student. If asked, blame it on some other kind of martial arts training. Bonus: through reenactment of the known physical movements you get faster access and control over your new body.

As a sidenote:

  • you body trained martial arts for 10+ years - so you are probably quite fit
  • you are in a males body

Most societies on earth are male-dominated and as a physical fit young man you might fit right in / have less to worry then you think regarding "survival".

I am no longer on modern Earth:
While but overall physical fitnes is always a bonus, your martial arts prowess might not be of much help if you are:

  • stranded on the frontline inside a trench in Word War I
  • locked aways in a city under quarantaine due to Black Plague in 1408
  • slaved to some oars on a galley in the middle of the mediterranean sea
  • stranded on an island ruled by amazons and delegated to a live as boy-toy

While focussing on the bodyly aspects of your marterial training you might also benefit from learning other aspects of "the way" your former body inhabitant followed: martial arts are often connected to a way of thinking and livestyle - if any of that bleeds over into your new self your may reap some benefits in that way as well.


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