a little bit more explanation to Steven Arbitman's (https://www.quora.com/Can-modern-science-reveal-evidence-that-denies-the-existence-of-energy-known-as-qi-or-chi-or-prana-not-by-stating-the-impossibility-of-measuring-it-but-through-reliable-methodological-standards/answer/Steven-Arbitman-1) and Melvin Dunn's (https://www.quora.com/Can-modern-science-reveal-evidence-that-denies-the-existence-of-energy-known-as-qi-or-chi-or-prana-not-by-stating-the-impossibility-of-measuring-it-but-through-reliable-methodological-standards/answer/Melvin-Dunn) answers.
energy means ability to perform some work. more energy, more work. there are a lot of different processes in our body. they are not the same as processes in mechanisms or computers, they are holistic. you can't take out damaged part and replace it with another. think it as a wave picture on a water surface, where each wave is spread over whole surface, while at local places you can see only peaks, interference result of endless amount of waves. even you replace some part of this surface, it will still suffer same problem with time. this is why western medicine have some problems, which it conceptually can't deal with. though these problems are easily solved by eastern medicine.
that infers processes in our body are somehow similar, compatible to each other. specifically our brain and nervous system can feel and reflect these processes in familiar terms, like cold/hot, colors, motion, breathe, pulsations etc. it is possible via training to better recognize these processes. moreover, by imaging these patterns it is possible to induce according processes. knowing a scheme of these patterns it is possible to purposely and effectively affect body processes. though it is not a fast way and each excercise takes a lot of time to make imagined wave pattern effective.
so these processes can be expressed as energy flow, performance of these processes can be corresponding to amount of energy, trajectories and peak points of these processes can be referred as channels and in/out points on our body. there are many kind of processes, correspondingly there are a lot of different kinds of "energy" and "points". some of them may correspond to western medicine concepts, some not. think it as higher-level concept. like running program hardly can be explained by measuring voltage changes on a particular chip. though at low level body processes can consist of chemical reactions, electromagnetic and even quantum processes, which can be dealt with western science.
weak energy flow, sealed channels/points means weak health. good energy flow, clear channels and working points means good health. qi gong excercises are directed towards gaining energy and channel clearing. also there is a possibility of transformation of energy from one kind to another, this is also big part of practice. for example, if you want to jump, run, fight and can't seat and think, means excess of low-lewel energy and lack of higher-level energy. excercices exists to convert one to another, i.e. making plodding and thinking instead of being restless. another big part is meditation, based on the same concept, but there considered mind processes.
some other techniques, like hatha-yoga, Alexander Lowen excercices and numerous embodiment techniques, also qigong, are using static body poses instead or together with imagination/breathing. these poses are also changing energy flow/body processes. correct pose can affect health positively, though it takes some time, up to several minutes to become effective.
external sounds and images (especially if you are looking/listening at) are also affecting inner body processes. the same is about electromagnetism.
this was a basic, rough materialistic explanation of qi. of course, it can be measured. for example we can raise temperature of our hands or change brain state via imaging proper schemes, which is measurable. also there are a lot of evidence and scientific research that qi gong and similar practices are affecting health positively.
also, there are evidence, that a brain, as a quantum device, can project its inner patterns to outer reality via changing it on quantum level. and vice versa it is possible to detect outer reality hidden patterns using a brain as a quantum receiver. conceptually nothing prevents to materialize entire objects and even whole worlds with proper training.
read more on this topic:
- my answer to What is a physical explanation for magic? (https://www.quora.com/What-is-a-physical-explanation-for-magic/answer/Dmitry-Bryliuk)
- my answer to What makes time, time? (https://www.quora.com/What-makes-time-time/answer/Dmitry-Bryliuk)
- my answer to How can I go about developing my mental toughness, grit and the ability to cope with adversity? (https://www.quora.com/How-can-I-go-about-developing-my-mental-toughness-grit-and-the-ability-to-cope-with-adversity/answer/Dmitry-Bryliuk)
- my answer to How can I motivate myself for workout 3 hours, study programming 4 hours and work 6 hours each day? (https://www.quora.com/How-can-I-motivate-myself-for-workout-3-hours-study-programming-4-hours-and-work-6-hours-each-day/answer/Dmitry-Bryliuk)