Alice was alone in her room. She was recovering from all the intensive training with Rachel. Her control of mana was becoming more natural by the day, but her physical condition was bad. She had been training against Rachel’s strengthening magic every time she came to the manor, and she managed to confirm that she could not rely only on her current kinetic armor: Alice was awfully slow. As such, what she needed was some kind of speed boost.

She had attentively observed Rachel using her magic and she was sure she could somehow emulate it. It would not be that easy, however. Rachel was lucky to have gotten a magic type that did almost all the work without her thinking about it.

As far as Alice understood this power, there was a good chance that, among many things, Rachel’s magic boosted the production of molecules known as adenosine triphosphate, or ATP.

On Earth, these were often called the energy currency of the body. With the breakdown of ATP, called ATP hydrolysis, a significant amount of chemical energy was released. Thanks to that, a process called a cross-bridge cycle could take place: a protein, the myosin, changed its structure and made another protein called the actin rotate. This was the origin of muscle contractions. Therefore, with more ATP, one could either produce more instantaneous power with their muscles or instead use those muscles longer, like in a marathon.

ATP could be naturally produced in a few different ways, like with the breakdown of glucose by oxygen in the case of aerobic respiration.

All in all, a greater production of ATP meant a greater stock of energy, so strengthening mages probably used this. To some extent, at least.

(I doubt I can increase my ATP with my magic type though…)

However, Alice had an idea to work around it. This myosin protein did not react to ATP hydrolysis specifically, but more to the energy that resulted from the molecular bonds breaking during this process. As such, she might be able to trick her body and forcefully activate the structural change of these proteins with her own mana that she would turn into a form of energy that resembled that chemical energy.

It was a much more direct approach than strengthening magic, but it could work. Well, as long as the process of muscle contraction was similar in this world. With such a technique, Alice would be able to have more powerful muscles and greater endurance.

There was just a tiny issue with this. To produce enough force to simply hold up a few hundred grams with one hand, quite a few myosins were required. Like, a few trillion of them. Needless to say, Alice would never be able to do so many operations consciously. An extremely intricate spell was necessary for that, and it would be much more complex than her mana armors.

She was confident she would make it work, but she was hoping it would take a few weeks rather than a few years.

Every day, before she went to bed, she sat at her desk writing and calculating things. Without doing anything, a ball of mana positioned above her was constantly and faintly casting a mana-to-light conversion and was recharging itself by occasionally tapping into Alice’s mana pool. With those freezing temperatures outside, the heat loss from this constant energy conversion was actually a good thing.

(So… In cells, I think ATP hydrolysis produces a few dozen kilojoules per mole of ATP. That is, for a few hundreds of thousands of billions of billions of molecules. Haaaaah… It might take a while...)

***

For two whole months, on paper, Alice tried to formalize a spell that could spread a specific input of mana throughout all her muscles. The objective here was to simply create a helper spell that would be used in the real strengthening spell, but Alice had trouble coming up with a fitting algorithm. Continuously spreading the mana was easy enough and she didn’t even need a spell for that, but the issue was that it shouldn’t be continuous. The mana had to be partitioned at specific locations in her body. In concrete terms, her body was a discrete coordinate system with an absurd amount of possible locations.

She had read a lot and even had had to ask Viktor to lend her his books about muscles in order to pinpoint precisely what points she should target with her spell to get only the muscles. Measuring the spreading of the mana in her body was so hard that she had to stay up at night so that there would be no sound interrupting her.

After those two months, the spell was finally finished, and Alice had turned fourteen by that time. The helper spell didn’t do anything besides spreading the mana in her muscles, but Alice was still incredibly proud. Once this nerve-racking spell was created and accepted by her magic type, the rest would be easier.

***

And indeed, only two weeks later, Alice had a complete spell at the ready. It was way easier to trick the myosin proteins than she had anticipated. As long as the mana was perfectly partitioned in a muscle, it acted as a sort of potential energy that these proteins wished to feed on.

(Surely, with this spell, I will be able to forcibly start the cross-bridge cycles and enhance the contraction of my muscles.)

After all, all the small-scale tests seemed to be a success. For larger-scale ones, she would wait for Serena as it might be dangerous. She expected to undergo some trial and error once she would deploy the spell on the macroscopic scale.

***

“True-pseudo-strengthening-magic: cross-bridge cycle version I, activate!”

“That name is awfully long…”

Even though Serena was criticizing her naming sense, Alice still looked super proud of herself. But then she froze and fell flat on the ground.

“Oh… Are you dead or something?”

“I-I cannot move! My limbs won’t move!! Why?!”

“Mmh… it really looks like what happens with dead people. You’ve hardened.”

“Y-you are thinking of rigor mortis…”

(Rigor mortis, caused by the lack of ATP in a dead body… But why? I’m making it so I don’t need their hydrolysis to start the cross-bridge cycle in the first place…)

Then, she realized what had happened. She had started the cycle, but she didn’t end it. As such, it wasn’t even a cycle anymore.

(Ah. I forgot to put back the myosins in their initial state… It needs energy for that too…)

If you come across this story on Amazon, be aware that it has been stolen from Royal Road. Please report it.

Without the necessary energy, the myosins wouldn’t let go of the actins, making it impossible for the next cycle to occur, and for Alice to relax her muscles.

After a few seconds, she was able to move again. The natural ATP hydrolysis that occurred in every cell had finally ended the cycles for her.

She spent a part of the following evening correcting this omission in her spell, and she was ready to try it out again with Serena for the next lesson.

***

“‘True-pseudo-strengthening magic: cross-bridge cycle version II’, activate!”

“Stop with that name already… Also, aren’t you just walking normally?”

“It sure looks like it, but I am not spending nearly as much chemical energy as I would normally.”

“How does the spell work?”

“When it detects a significant contraction of a muscle, that is, a voluntary movement, it takes over to proportionally assist the muscle contraction by activating all the myosins nearby with mana instead of ATP molecules and their hydrolysis. When I stop contracting myself, the assistance ends too.”

“Myosin? Ayteepee? Here you go again casually dropping strange words… Is it really multiplying your strength?”

“You could say that. However, it cannot go beyond the limit of my muscles like with a strengthening mage. If I put in more mana than my muscle fibers can withstand, the stress will be too high and something will definitely break. There is no reinforcement for my muscles and bones, so it is merely an emulation of only one aspect of strengthening magic.”

Again, Alice still seemed very proud of herself. She had tried her best to create her most optimized spell yet.

“Then, just call it 'strengthening emulation' instead of this ‘true-pseudo-strengthening magic’. I didn’t say a thing about the names you gave to your armors of mana, but you’re pretty bad at naming things.”

“W-wha-? What do you have against my kinetic and photon styles? They are cool!”

“Cool? What about the name you gave to your mana-recovering spell?”

“‘Ortu Solis’? This one is probably my best name yet! What do you have against it?!”

“That’s just nonsense! It doesn’t mean anything!”

“It does! In a certain dead language, it means ‘Rise of the Sun’ or something!”

“What does ‘Sun’ mean, then?!

“Ah. Good point. It uses Hiphus’ light, not the Sun’s… How about ‘Ortu Hippus’ in that case?”

“That’s worse!”

“You are getting annoying... It is because you have only one spell that you cannot understand how good it feels to give a cool name to every one of them.”

“Y-you little-”

“Catch me if you can! I will make you understand why my ‘true-pseudo-strengthening magic: cross-bridge cycle version II’ is the best name!”

Serena tried to catch Alice, but the little girl was incredibly fast. Mia, who had been reading a book near a tree, raised her head upon hearing her master laugh and was shocked. Alice had clearly never run as quickly as now, and she didn’t even seem to be tired after several seconds.

With a little bit of her own ATP, Alice was spending about as much chemical energy as if she leisurely walked. With the assistance of her spell, however, she was uncatchable.

(I might call this ‘Lightning Speed’ after all! Ah, wait, I’ll probably use it for strength-related tasks too, so I can’t…)

Indeed, she could even freely choose the intensity of the assistance. With a low value, she would be able to easily run several marathons, while a high one would let her produce great instantaneous power.

So, Alice decided to choose a definitive name later on.

***

“A cramp? Again? What’s wrong with you today?”

It had been a week since Alice had used for the first time the ‘true-pseudo-strengthening magic: cross-bridge cycle version II (temporary name)’.

Since then, although she had made some progress and could use it even more naturally, she now seemed visibly weaker than before. Just now, Alice had had a cramp for the third time during her lesson.

“We’re done for the day. Just rest for now. What kind of disease do you have? Did a doctor examine you?”

“I-I wonder what that could be…”

“Wait. I know that face.”

“Eh?”

“Are you lying, by any chance?”

“W-what are you say-”

“Do you actually know the reason for your current state?”

“I-I know nothing!”

“Spill the beans already!”

(What betrayed me?!)

Truth was, Alice was really bad at lying. After a full year of tutoring, there was no way Serena wouldn't realize when Alice was making things up.

“I… I think I am low on calcium…”

This spell had another downside, and it was probably the worst according to Alice. Calcium ions were in fact as necessary as the ATP supply for those cross-bridge cycles to occur. Alice had succeeded in replacing the ATP with mana, but she couldn't do anything to replace the calcium ions. After a week, she had used up most of her stock and was suffering from hypocalcemia.

As such, Alice would have to add a lot of food rich in calcium into her diet, like spinach back on Earth. The thing was, Alice hated midranate, the leafy green vegetable that resembled it the most. It was to the point that she had been trying to forget about all of this. Incidentally, her former self hated spinach too.

Frankly, her aversion to those kinds of vegetables was so strong that she was considering giving up on this strengthening emulation spell. At least, she did not mind nuts, which contained some calcium too.

All of this was a shame because, apparently, strengthening mages didn’t have this issue at all.

(Those bastards… Do they use some other way to keep their calcium ions that I don’t know, then?! Just tell me how to do it too!)

Maybe their element did some work in the shadows. As Alice reluctantly told all this to Serena, the latter had a creepy smile on her face.

“Alright, you stay here and take a rest. I have some things I need to do.”

“Nooooo! Whatever you are thinking, please don’t!”

“Catch me if you can!”

Serena started to run in the direction of the mansion, where Alice’s parents were.

Weak as she was, Alice was much too slow to catch Serena. She tried to apply her spell by forcibly activating her proteins with mana, but instead of explosive speed, she got her fourth cramp of the day and fell on the ground.

“C-come back!! Mia, please catch up to her!”

“I am sorry, Lady Alice. I am afraid I have not yet found the perfect stopping point.”

Then, her maid proceeded to keep reading her book as if nothing happened.

“Dammit!!”

***

At dinner, Alice was taking glances at her parents' expressions to see if Serena had really told them about this. However, they seemed normal. The menu was the regular one too so, in the end, Serena had probably called it a day and left the manor as soon as she could. Alice sighed in relief and spent a marvelous time eating what she loved.

The day after, however, as she descended the stairs to eat breakfast with her family, she saw a plate full of midranate, the closest equivalent to spinach in this world. It was served only on her plate.

(N-nooooooo!)

She screamed inside while trying to keep a stoic face, but everyone could tell she wanted to cry. If it was only a one-time thing, she might have been able to tolerate midranate. However, she was certain she would be forced to have this regularly.

For the next few days, Alice was forbidden to use her magic and was forced to eat lots and lots of midranate-based meals. She ate so much of it that she was starting to get the symptoms of another condition called hypercalcemia, the opposite of hypocalcemia. Surprisingly, some of the symptoms were very similar, like all the cramps Alice had in her legs and her general weakness.

She tried to convince her family and the cooks that she had the same symptoms again but this time because they gave her too much midranate to eat, but everyone was accusing her of throwing up in secret after her meals.

(If this goes on, I’ll have kidney or heart problems…)

In the end, Alice had to secretly deplete the excess of calcium she had by using her strengthening magic emulation for a few hours straight. Her mana gave up before her calcium ions, this time.