Robin Wang has recently been exploring the connections between qi and moral psychology in early Chinese thought. Among other things, she notes the importance of caring for the body in the tradition -- both the moral obligation to do it but also, perhaps, the asserted connection between moral goodness and physical health. (One index of the importance of that connection in the ancient Chinese tradition is the frequency with which it is mocked by Zhuangzi.)
Confucius (if the passage is authentic) notes the connection between morality and qi thus:
There are three things the gentleman should guard against. In youth when the blood and qi are still unsettled he should guard against the attraction of feminine beauty. In the prime of life when the blood and qi have become unyielding, he should guard against bellicosity. In old age when the blood and qi have declined, he should guard against acquisitiveness" (16.7, Lau trans.).Thus, disorders of qi are associated with a propensity toward certain moral failings. Mencius even more famously associates a "flood-like qi" with moral rightness (2A2).
There is something attractive in this view. It's uncontroversial that peace of mind is good for your health, and it's very plausible that health is generally good for your peace of mind. It may be hard to muster up the energy or will to do what's right if one is feeling substantially less than vigorous, and certain types of physical shortcomings may lead us more easily to certain sorts of moral temptations.
Yet at the same time, a concept that intimately connects physical health and moral health strikes me as highly noxious. Is the highest degree of moral propriety impossible from a wheelchair, or from one's deathbed, or from someone with chronic fatigue? It seems to me that physical disability often gives as much to us morally as it takes away (e.g., by increasing our sympathy with others or by broadening our perspective).
What the connection is between physical health and moral behavior is an empirical question, of course, but one that would be very difficult to study well. I've heard of no studies. (And any one study, anyway, would have to be highly limited.) In the meantime, I say down with the concept of qi!
P.S.: For those readers interested in Chinese philosophy who haven't noticed it yet, I recommend Manyul Im's Chinese Philosophy Blog.