Hypothetical fitness question? Based on 2 peoples fitness levels and the jobs

Im not qualified in this however this is my understanding of fitness.

Fitness is a measure of how quickly someone returns back to THEIR normal resting heart rate. If both these people can run the same distance etc well that means very little until they stop, then its a case of who returns to their resting heart rate faster, as a fitter person's complete cardiovascular system (lungs, blood flowing oxygen etc) will be more efficient in supplying much needed oxygen back to the heart etc.

The more you exercise the more at a higher intensity or for a greater amount of time, the more mitochondria are created inside your minute cells. These are the batteries in our cells. Now all your cells will use these batteries however during your normal working day, unless you are pushing your body there will be little need for the cells to activate these at complete 100% power on as such.

So when you are running these are activated in supplying you energy, thus as a person runs if he feels it isnt so strenuous when someone else does he can do more work ie faster running or longer duration, this is also an indication of fitness, and these then work to help you maintain your running, when you stop then its a matter of your cardio system to supply you with enough oxygen to all your cells for the cells to function, for the mitochondria to function and the energy production in the ATP klebs cycle, thus fitness overall isnt about who can run faster or who can run further only but who can recover faster.

As you train more you recover faster, say you can run 10miles and it take 5mins to recover, well logic dictates that with enough practice you will eventually run 10miles alot easily because you wont feel so stressed thus meaning you will recover quickly since you wont be pushing your heart beat as fast as before, so its about recovery time.

I hope that all makes sense

ps: even if you work strenously at work, perhaps you recover faster due to eating carbs/sugars/bananas supplying your muscles and body with energy so that when you run you already have enough inside to keep up.

I will add that if you are working strenously and can keep up with others then it does imply better fitness, however you should run when both have a day or 2 off so its more equal to measure and guage

if they can both run the same distance in the same amount of time, the only other factor affecting their fitness is their heart rate, which you havent mentioned. you cannot say one is fitter than the other