Chi-kung is a very versatile practice as far as a practitioner's objective is concern. In Hong Kong and mainland China, there are many practitioners who do it for its benefit of boosting up their immune system. I'm talking about people using chi-kung as a supplement to modern medicine or a cure of last resort.
Mi Jingke (秘静克) a lineage student of I-style Grandmaster Wang Xianzhai (王薌齋), age 90+ is teaching zhan zhuang (standing meditation) in earnest in mainland China with this objective in mind. She does it in association with public hospitals there. In her new Chinese book "The foundation practice of Dacheng Kungfu"(大成拳築基功), she mentioned that most of her students (patients) were seeking cure of last resort from learning and practicing zhan zhuang, which she would individually modify to suit each patient's state of health as well as nature of illness. Mi's practice regime is very vigorous. She demands her patients to practice zhan zhuang (individually modified version) minimum three sessions a day, with 30-40 minutes per session! And according to Mi, some of her more "devoted" patients practiced five times a day. In a hospital environment, Mi is expected to deliver noticeable results within some 16 days. And according to Mi, more than 90 percentage of her patients who did go through with 16 days got noticeable results (with some 70-80% did go through the period). In some cases, her patients were also helped with acupuncture, and all continue with their regular medical drugs (mostly western medicine). In her book there are many testimonials, and as if she could feel that her readers might doubt, it included images of some of her patients' personal writings!
Testimonial is indeed not a scientific method to establish the efficacy of a new drug or a new treatment method. But unfortunately, it is the only way to demonstrate the effectiveness of using chi-kung (in this case zhan zhuang) as a cure of last resort. For one thing, a random selection of testing subjects is impossible: without a belief in the system, a student can never attain the mental state able to generate enough chi; not to mention the requirement of a diligent practice of 3 times a day, 30-40 per session - not easy to achieve even for healthy students. Besides, unlike the testing of a new drug, placebo is impossible to be employed in the case of chi-kung!
The modern rational man will likely find it uneasy to put "faith" as a prerequisite for a practice that claimed to have powerful effect as a "cure of last resort" (one necessary mention here: Mi Jingke was not specifically refer to terminal illness, but mostly refer to long-term illness that can't be effectively cured by our medical practice to the satisfaction of the patients). Therefore, if you're are still following me and not considering me talking about irrational "cure by faith" as practiced by some "gurus", please read on!
One essential requirement (as Mi mentioned in her book and I can testify to be necessary according to my own coaching experience) is that a high-impact continual practice is required to gain noticeable effect. During an intense practice session, one's chi will be generated to a high level inside one's body. After the session ends, chi will gradually leave one's body. The key to success is: just before chi goes down to too low a level, the practitioner (patient) is required to start another session - resulting in an effective concentration of chi being inside one's body almost 24 hours a day!
What causes the curing? In the lingo of classical Taoist thinking, it is one's natural curing power (in the form of chi) being activated that has a capacity to cure any illness. And in the lingo of modern medicine, it is one's immune system being boosted up.