We are a commune of inquiring, skeptical, politically centrist, capitalist, anglophile, traditionalist New England Yankee humans, humanoids, and animals with many interests beyond and above politics. Each of us has had a high-school education (or GED), but all had ADD so didn't pay attention very well, especially the dogs. Each one of us does "try my best to be just like I am," and none of us enjoys working for others, including for Maggie, from whom we receive neither a nickel nor a dime. Freedom from nags, cranks, government, do-gooders, control-freaks and idiots is all that we ask for.
When I discuss fitness and conditioning, I use the categories of Strength Training, Endurance Training, General Athleticism Training, and Nutritional "Training."
Naturally, different regimens address each fitness category with some specificity but with some overlap. To get stronger, you have to stress nerves and damage muscle fibers by moving weight. For endurance training, 20 mins of intense interval exercise seems to beat out longer low-intensity aerobic cardio. All categories feed into General Athleticism which is most peoples' real goal - Fitness for whatever life brings - but we address it specifically with calisthenics and by playing recreational sports and other outdoor vigorous activities.
These categories of activity use different combinations of energy systems. Animal bodies have three energy systems, each with different purposes.Just as nerve pathways can improve with stress and challenge, cellular energy systems can be bolstered with stress. When you think about it, a fair amount of stress is good for both body and soul.
Your energy systems are the Phosphagen System, the Gycolysis System, and the Aerobic Oxygen System. In a balanced Conditioning regimen of Strength, Endurance, and General, all three energy systems adapt to being stressed and, ideally, exhausted. Your body will build up those systems, over time, to meet the challenge. That is called "more energy."
For one example, the Phosphagen metabolic system can be stressed or depleted by ten heavy ball floor slams or by a 30-second full-out sprint. That system is for quick bursts of maximum power.
This site, The Three Metabolic Energy Systems, explains the basic physiology of the three energy systems with a discussion of how each is best stressed (but unfortunately that discussion only addresses things like running rather than the other exercise categories which also make specific demands on the 3 energy systems).
While the human body is complex understanding energy and stamina really isn't complex. It is a simple system of glycogen and oxygen delivery where and when needed. It takes years of training to expand the lung capacity, and the ability of the heart to deliver more oxygen rich blood. To enlarge arteries and veins to accommodate the increased oxygen enriched blood flow. And it takes regular and almost constant physical activity to condition the muscles and the liver to hold larger supplies of glycogen (sugar) readily available to power the muscles.
Most "doping" in athletic events is all about either getting more oxygen or more glycogen to the muscles under extreme endurance conditions. It is like putting a supercharger on a car or using a fuel containing nitro to improve performance.
It really is that simple: Get more oxygen and glycogen to the muscles and get rid of the waste products more efficiently. The only way to do it is months and years of training (although good genetics and youth help a lot). The human body is malleable and we are constantly shaping it and changing it for better or worse.