The two fought inextricably, the battlefield was like the end of the world, not to mention living creatures, even the hard stones were constantly shattered, and no one dared to stay for a long time within a radius of miles.

Of course, Zhang Curtain doesn't count, he hides deep underground, and even the two sides of the battle don't know that there is a bold guy watching with relish at his feet, if he knows, he must be killed first, so as not to have an accident.

Zhang Mu gained a lot, and through some observation, he found that the cultivation of the woman who called Su was weaker, but the swordsmanship was amazingly fast, and the sword qi condensed to the head of the sword, breaking the face with a point, so that the young man was afraid to dodge, and for a while he had the upper hand.

"She wants to end the fight as soon as possible, and the other party wants to fight steadily, and the result depends on who can succeed!"

Zhang Mu saw a little bit of the situation and waited without impatience, he had to wait for the two of them to finish fighting before he dared to leave.

Half an hour later, the two were still fighting, Zhang Mu was helpless, because there was no air underground, he had been holding his breath, and now he was a little uncomfortable.

He estimated that he would hold it for another half an hour at most, otherwise he would have to die, he had not yet succeeded in establishing an independent circulation in his body at the moment, and he was still more dependent on oxygen.

Another ten minutes passed, Zhang Mu's face was flushed, he didn't breathe for a long time, and even if the control of life activities weakened, the oxygen in his body was about to run out.

"Why don't you fight elsewhere, my God." Zhang Mu screamed bitterly in his heart, if he wanted to watch the strong fight at first, now he didn't mean it at all, if the two of them didn't leave, he wouldn't dare to go up and change his breath.

"I secretly used my telekinesis to make a small hole and get out, so I shouldn't be discovered." Zhang Mu reluctantly separated some of his mental power, drilled the dirt open, and walked into a thumb-sized hole, spreading outward little by little.

He didn't dare to do it too quickly, but now he was under the eyelids of the two strong men, and once he was discovered, he would be miserable.

One meter, three meters, ten meters, just when Zhang Mu's face showed joy, there was a loud bang, the ground sank, and the hole he quietly hit was suddenly crushed.

"Damn, can't you just move to the side?"

Destroyed by the aftermath of the battle, Zhang Mu could only come from in a depressed manner, and the hole he made was easily destroyed, not because his mental power was weak, but because he had too little mental power.

He was more than twenty meters deep into the ground at the moment, and the pressure of the soil was very terrifying, most of his mental power was used to support the soil, and some of it was used to hide his breath from being detected.

As for using the True Qi, he didn't dare to mess around, the fluctuation of the True Qi was too obvious, and it was estimated that even twenty meters of dirt might not be able to block it, and he didn't want to take any risks.

As a result, he could use less than one percent of his mental power to make a hole, and the soil was too heavy, so he could keep the hole from collapsing for a short distance, but as soon as he left ten meters away, he was a little powerless.

He had to try another angle, but if he was unlucky or not, there was always an aftermath that fell near him, shattering the hole he had just punched.

"Damn, are you so unlucky?"

Zhang Mu was speechless, tried a few more times, but still failed, and the time he could hold on was running out.

"Why don't you get closer to the ground?"

"It's too dangerous, the two are fighting, they must be sensitive to the nearby situation, and it is easy to be discovered."

Zhang Mu's face was cloudy, and he wanted to dig a little to the side, but found that the soil here was terrifyingly hard, and it was simply unrealistic to leave horizontally.

"I thought about picking up the bargain, but I ended up pitting myself." Zhang Mu sighed, he didn't expect this situation at all, he really just wanted to watch the play.

"There are still more than ten minutes, I will try to see if I can replace the effect of oxygen with true qi and establish a more advanced internal circulation, if not, I can only take the risk."

Zhang Mu can only change his thinking, the two people on his head are extraordinary seventh-order existences, their cultivation is unfathomable, and they are supplemented by the vitality of heaven and earth, and it is a trivial matter to fight for a few days and nights, and they want to leave secretly after they fight, but now I am afraid that there is no chance.

The thought was withdrawn from the outside world, and only the power to hold up the soil was retained, and Zhang Mu's mind was all in his body, and he was forced to try one thing that he should cultivate next.

In ancient times, this step was also called fetal breath, which means that if you do it, you can survive in another cycle like a baby in the mother's body.

But in fact, the fetal breath of martial arts is still different, because the baby essentially uses the mother's oxygen, and this step is to abandon the effect of oxygen and let the human body get rid of the needs of the outside air.

This step is to use the special energy of true qi to replace oxygen molecules to participate in the life cycle, so that the metabolism in the body is independent of the outside world, and it is really possible to survive for a long time without eating or drinking, and only need to replenish vitality.

It can be said that as long as this step is achieved, even if you go into space, you can survive for a long time without relying on a spacesuit at all.

"I have enough theoretical knowledge and hope to succeed."

Zhang Mu said secretly, his mind fell between the dantian and the lungs, especially the lungs, and his mind desperately sank to the subtleties, and soon felt the existence of small tissues.

Dense dark alveoli appeared, the alveoli had shrunk a little due to the lack of breathing, and the carbon dioxide in the blood had reached a very high level.

He must use True Qi to simulate oxygen molecules, so that True Qi can be like oxygen, which can allow biochemical reactions in the body to obtain enough intermediate substances.

This process is very simple, but the strength is simply rare and perverted to operate, you must know how tiny the molecule is, even if his mind is weak to the extreme, it is only to the same extent.

"Let's simulate some oxygen molecules."

Zhang Curtain concentrated, outlining the true qi little by little, but it had just taken shape, and it was broken with a bang.

In the microcosm time, the time has been greatly extended, and there is still a lot of time for the curtain, so I am not in a hurry to try again.

In fact, he had tried to break through many times before, but each time he ended in failure, and the fetal breath realm had no absolute relationship with cultivation, and it didn't have to be achieved immediately, and he didn't do it too deliberately.

If he hadn't been forced by the situation now, he would probably have to try slowly while improving his cultivation, as long as he did it before his cultivation reached its peak.

"I need oxygen now, make one for me!"

Zhang Mu felt the discomfort of his body, and the slightest trace of true qi continued to merge and transform, and he tried hundreds of times in a single thought, but he still failed.

Molecule-level things, if they want to be completed by personal thoughts, it was almost impossible in the past, but this is indeed a threshold in the martial arts, and most of the generations have been stopped, and many people have crossed it.

Zhang Mu knows that someone can do it, so he keeps trying, this kind of thing others can fail countless times, and he can do it the same.

After a few minutes, he eagerly tried tens of thousands of times, but there were still some things missing, and his true qi was too unstable, even if he had a model next to him, it would be difficult to take shape at once.

"It's really difficult, don't forget it, some people haven't reached this realm, but they can still break through to the next level."

Zhang Mu was a little discouraged, to be honest, if it weren't for the need for internal circulation instead of breathing at this moment, he probably wouldn't have paid too much attention to this matter at all.

(End of chapter)