Never before had Li Yundong, in his former life as an indoor enthusiast, considered that even eating and sleeping could be a form of cultivation, let alone running!

After Li Yundong read the Huangdi Neijing, although he couldn't fully grasp all of its contents immediately, he forced himself to commit it to memory using his phenomenal recall, certain that he would slowly understand it as time went on.

When he first started running, Li Yundong felt nothing unusual in his body because it had been fundamentally reshaped by the Renyuan Golden Elixir, granting him immense power not only in strength but also in adaptability and endurance.

Where an ordinary person could lift one hundred jin, Li Yundong could lift one thousand. Where a normal person would gasp for breath after running five hundred meters, Li Yundong could sprint a full five kilometers without his complexion changing or his breath quickening.

However, once Li Yundong started running nearly ten kilometers while carrying the hundred-plus-jin Seven Treasures Spirit-Guiding Fan on his back, he began to feel a steady thermal vapor rising within him. This heat continuously swelled, churning violently within his chest and viscera.

This sensation was intensely uncomfortable at first, mirroring the feeling he’d had when he’d lost control and sprinted wildly back in school. It was as if he had become a pressure cooker, brimming with expanding heat. The more he ran, the more bloated he felt, to the point where Li Yundong desperately wanted to rip off all his clothes and split open his own chest just to let the pent-up energy escape.

Li Yundong desperately wanted to stop and let the internal energy settle, but he suddenly recalled Ziyuan’s instruction: never stop during the first run; push as far as you possibly can, until you truly cannot take another step.

Li Yundong gritted his teeth, lowered his head, and forced himself to continue. After another five kilometers, Li Yundong had already left the city limits. He began to feel a burning heat all over, and every one of his thirty-six thousand pores felt as if it were being pricked by needles, a sensation that was both painful and intensely itchy.

Li Yundong couldn't help but feel a jolt of alarm, unable to comprehend why this was happening.

But after a moment of thought, recalling the Huangdi Neijing he had seen, he unconsciously began to search the knowledge stored in his mind to self-diagnose the phenomenon.

After searching for a while, Li Yundong could no longer bear the feeling of the frantic, boiling heat surging inside him. All his pores opened, and sweat began to pour from his body.

As the sweat broke, Li Yundong immediately felt some of the suffocating heat inside him dissipate. His spirit soared, and a sudden realization struck him, as if he were finally beginning to understand Ziyuan’s reason for telling him to cultivate his physique through running.

Li Yundong had an epiphany: when the body’s pores open, the vital yuanqi flows outward. Running, however, forces all the muscles and internal organs to move, compelling the pores to open and expel the yuanqi from the body.

Yuanqi is a person’s most precious essence. According to the theories of longevity, the amount of yuanqi one is born with is fixed; it cannot increase, only diminish. Some people are born with ample yuanqi, while others have little, like comparing a large gas canister to a small one.

As he ran, Li Yundong mused to himself, bearing witness to his self-comprehension: those who do not know how to cultivate cannot increase their inherent yuanqi; it only wanes with the passage of years.

Why are children’s eyes dark and bright? Why do many people’s eyes become duller as they age?

Because children possess the fullest yuanqi, their eyes are dark and bright. As years pass, if one neglects the nurturing of body and spirit, the yuanqi within the body is lost, causing the eyes to lose their luster.

In the practice of longevity, controlling the yuanqi to prevent its easy leakage is paramount, and one of the most crucial tenets is this: never induce heavy sweating!

When people are young, their yuanqi and energy are at their peak, so they often ignore this point, frequently sweating profusely as if they just stepped out of a shower. Little do they realize this is a severe depletion of their vital yuanqi.

Li Yundong continued to run, these thoughts cycling through his mind. He was an exceptionally intelligent man; Ziyuan had only offered a slight hint, and he had already made a conceptual leap, clarifying many issues at once.

He reasoned: Why is it that many athletes end up with poor health in old age? They might have this ailment or that one. While a portion of this is due to the physical damage caused by high-intensity training, a far more crucial reason is that they sweated excessively in their youth, opening their pores too widely, severely wounding their yuanqi, leaving them hollow and without internal support in their later years.

Furthermore, why do many frail individuals become dizzy and lightheaded after taking a long, hot bath?

Because the pores remain open for too long, allowing the body's yuanqi to escape.

With this realization, Li Yundong had unconsciously covered another five kilometers. Before, running two kilometers would have left him panting and exhausted, but now, Li Yundong only felt his internal energy surging, his entire body operating like a high-speed motor. The internal energy "thump-thump-thumping" drove his body forward, making him feel stronger and more comfortable the further he ran.

At this point, Li Yundong finally understood what it meant when Ziyuan said, "Running is also a form of cultivation."

Ordinary cultivators fear sweating and opening their pores because they dread the leakage of yuanqi.

But Li Yundong was different; he now feared that the boiling, churning yuanqi inside him had nowhere to go. Like a pressure cooker, if the heat constantly builds and expands, the entire vessel will explode. But if there is a vent to release the steam, the vessel will remain intact.

With his movement and sweat, the churning heat inside Li Yundong immediately found an outlet. He had transformed into a massive covered tripod furnace.

Ge Hong, the grand master of the Alchemical Furnace School during the late Eastern Han Dynasty, believed the human body was a great tripod furnace. To cultivate the inner elixir, one must use Jing (essence) and Qi (energy) as medicinal guides, refined by Shen (spirit), ultimately forging the body’s internal elixir!

The foundational effort of cultivation, Zhuji (foundation building), is precisely the process of refining the body’s essence and energy into the inner elixir using the spirit.

Ziyuan had previously noted that the Zhenqi within Li Yundong was vast but lacked cohesion. Now, with this vigorous running, his internal Zhenqi surged and rolled. His entire body became a pressure cooker, creating immense internal pressure that continuously scoured his meridians and compressed his Zhenqi.

The principle was much like stewing bones in a pressure cooker: without it, meat and bone might take nearly an hour or two to become fully tender. But with a pressure cooker, once steam builds up, the bones yield in no time.

Li Yundong’s body was like that pressure cooker at this moment, and his internal Zhenqi was the meat and bone!

Unknowingly, Li Yundong ran along the main road for nearly thirty kilometers straight. It was high noon, and Tiannan City, being a southern metropolis, was already scorching in June. Now, under the blazing sun, Li Yundong looked as if he had been pulled from a pool of water; there wasn't a dry spot on him. Where his foot landed on the paving stones of the sidewalk, it left a clear footprint!

Despite being drenched in sweat, Li Yundong felt no fatigue; in fact, the more he ran, the more vigorous he became, and the brighter his eyes grew.

During the run, Li Yundong could not only feel his internal Zhenqi being beaten and impacted like fine steel tempered by a thousand hammers, but he could also distinctly feel his viscera constantly churning, vibrating against the internal heat.

Li Yundong couldn't help but ponder again: Why do so many people who love exercise rarely get sick?

Because when they exercise, their internal organs churn along with the movement. Although this churning is nowhere near the extent of muscle movement, it is still a form of exercise. Every movement draws the body’s yuanqi to gather around these organs, making them continuously stronger.

The principle is the same as for singers who must constantly practice their voices; it doesn't matter if they initially strain their throats, because the vocal cords become stronger and thicker with practice.

The internal organs of the human body follow the same logic.

Li Yundong knew that the constant churning of his internal organs was replenishing them with yuanqi. This kind of conditioning was a hundred, perhaps a thousand, times stronger than what ordinary people experienced.

Under the medicinal power of the Renyuan Golden Elixir, Li Yundong's one hour of training was equivalent to a common person training for a month; one day of his training was equivalent to a year for others!

When Li Yundong ran another ten kilometers this way, he began to feel a dull, rumbling sound emanating from his abdomen.

At first, Li Yundong thought he was just hungry, but he soon realized something was wrong because the sound inside his belly grew louder, and each rumble caused a sensation of his body vibrating. The sound was like distant thunder, deep and muffled, or like the roar of a tiger or leopard deep in the mountains.

"Could this be the Tiger-Leopard Thunder Sound?" A thought flashed through Li Yundong's mind.

As a dedicated homebody, Li Yundong had started reading Jin Yong’s martial arts novels since high school and remained a wuxia enthusiast to this day. He was certainly familiar with the concept of the Tiger-Leopard Thunder Sound (Hubao Leiyin).

Li Yundong recalled reading The Vanished Martial Arts World, written by Li Zhongxuan, the final disciple of Xingyi Master Shang Yunxiang. In the book, Li Zhongxuan asked his master, Shang Yunxiang: What is the Tiger-Leopard Thunder Sound?

Shang Yunxiang placed a cat in Li Zhongxuan’s hands and said: This is the Tiger-Leopard Thunder Sound.

Li Zhongxuan suddenly understood.

Cats, leopards, and tigers all belong to the feline family, and they share one common characteristic: their bellies constantly emit a low, deep sound. This sound is the continuous movement of their internal organs, resembling distant rolling thunder, hence the name Tiger-Leopard Thunder Sound.

The muffled sound in Li Yundong’s abdominal cavity right now was the "Tiger-Leopard Thunder Sound," a state that many martial artists fail to achieve even after years of effort!

Both cultivators and martial artists spend years, sometimes decades, striving to cultivate the Tiger-Leopard Thunder Sound, driving their skill deep into their internal organs. Yet, Li Yundong achieved it in a single day!

While shocked and amazed, Li Yundong marveled at the divine efficacy of the Renyuan Golden Elixir; without it, he suspected he would never have achieved the Tiger-Leopard Thunder Sound in his lifetime!

As his internal organs churned, Li Yundong distinctly felt his bones and muscles constantly swelling. This swelling was not painful; rather, it was filled with a sense of power.

Li Yundong could sense the energy within his body circulating rapidly. A portion of this energy vented out through his pores, purging excess vitality, while another portion propelled his blood flow at an accelerated rate.

This sensation made Li Yundong feel increasingly comfortable and energetic the longer he ran. His speed during this run had reached the pace of an ordinary person’s hundred-meter sprint!

This terrifying velocity stunned some drivers passing by on the road, nearly causing accidents.

Li Yundong suddenly realized: perhaps this session of cultivation was not an extremely arduous journey after all. On the contrary, he found himself immersed in it, unable to stop!