Normally, Lucas wasn't very motivated to learn about the biological sciences, instead preferring the precision inherent in physics or astronomy. But the possibility of knowing just how long the zombies might last before collapsing was rather exciting, and motivated his initial searching upon the Internet.
Originally, he had arrived at his conjecture via a hazy memory of a snippet of science he had either read or heard somewhere. Now he was perusing websites to recover that tidbit of crucial information so he could predict how long the crisis would last. Muscles required oxygen to work, but just how much they needed and how long they could last without it was unknown.
Whether the zombies would last for hours or days, Lucas wanted to have some sort of answer in mind before he returning to the people downstairs. Even in the worst case scenario- if his conjecture was wrong and the zombies still had a functioning circulatory system- Lucas figured they would grow weaker after a few days with no water just like a normal person would.
Possibly sooner because they seemed to be expending an awful lot of energy to move. And were probably working up a sweat in doing so. Lucas didn't watch the zombie at the front door for long, but from what he did see of it and others in videos so far had made them look extremely energetic. All that energy had to come from somewhere. And it had to run out eventually.
After skimming a few sources, Lucas found the science he had been interested in. Muscles used a chemical called ATP in order to move, which was created by mitochondria using oxygen. From what he could tell, ATP didn't seem to be stored and was used as soon as it was made. That meant that the body needed a constant supply of oxygen in order to make more ATP. That was the reason why vigorous exercise would lead to an increase in heart rate. More activity meant more ATP was needed.
But there was another way to make ATP when oxygen was scarce. Since the zombie with the missing arm couldn't be relying on oxygen carried in its blood, Lucas figured this had to be what was going on in order for it to remain active. According to the sources, this second method left acids and other byproducts in the muscle tissue, making muscles less effective over time. Although the websites didn't appear to be certain, this was also explained to be the reason muscles would eventually ache and sting after exercising for a while.
Using this basic knowledge, Lucas figured there was now a simple way to provide a rough estimate for zombie longevity. Assuming that they didn't have a heartbeat, it seemed reasonable to Lucas to assume that they would grow weaker in the time it took someone to start feeling exhaustion from a constant run. After a little longer, it seemed reasonable that they would collapse completely.
Lucas would feel worn down after a couple minutes of solid running, but he knew that he wasn't in the best of shape either. He speculated that it would be something that would vary at least a little according to the individual's fitness level. Although without blood supplying oxygen and removing the buildup of byproducts that point should really occur sooner in a zombie than it would in a person. That meant that absent a pulse or blood, a zombie's lifespan would probably be measured in minutes, rather than hours.
Thinking back to what he had learned of the outbreak from the news and other sources, Lucas reluctantly concluded that if they did not have a beating heart, then most of the original outbreak victims should have been rendered motionless by now. That meant that their hearts must still be working. The conclusion was a little disappointing and made Lucas feel silly about initially assuming they all would have no pulse. He couldn't really do anything with what he had read, but he at least felt some kind of assurance in having access to the science.
Luckily for the person trapped in that car, the zombie missing its arm and a good deal of its blood would have certainly grown weaker and stopped moving by now. If she really had been moving around for ten minutes before the recording had begun, then she probably couldn't have lasted for much longer. Maybe. Lucas attempted to find the video again to see if it eventually resulted in that outcome.
After a few minutes without success, it occurred to Lucas that there was a zombie right outside the front door of the dorm. Supposedly, blood loss should be capable of rendering it harmless within minutes. If only he could figure out a way to do that. Standing up from his computer, and pacing about his room, Lucas mumbled. "Too bad there isn't a safe way to test it."
Lucas decided to head downstairs again. He dug around for his glasses, wiped them off and locked his door on the way out.
