According to the article, the fish uses an ingenious method to generate warmth. The opah traps warmth from its flapping fins, which are well insulated by fat. The propelling fins in every fish are necessarily the most efficient and strongest muscles. Without propelling ability the fish cannot survive for long. In humans, the most efficient and strongest muscles is his breathing muscles, without breathing, he will die.
In other fish, energy generated by the propelling muscles is used for propelling only. The muscles are not linked to other operational duties nor heat thus generated being saved. The same for fish the same for an untrained man! Opah is genetically special. Chi kung needs to be trained.
Opah is different, its fat insulation trapped the heat energy. According to the article, the fish uses sophisticated thermal engineering (how sophisticated it is was not explained in the article) so that its muscles were consistently about 5C warmer than the surrounding water, with head region and heart about 3C warmer. A warmer head region makes cognition, presumably low-level, possible.
What happens to the practitioner of chi kung? A chi kung student, by using his breathing muscles to connect his other body parts, can generate and transmit both heat and motor energy to the rest of his body through long distances. Though we do not know the sophisticated thermal engineering theory behind the fish, the mechanism in chi kung can empirically be experienced by a student of chi kung. Typically a chi kung practitioner uses his own body to experience, experiment and manage such transmission system. For him, chi kung is both work-done and perfection of his chi-machine. And chi is simply the name of his empirical tool. He can feel it, not that he can always explain clearly to non-practitioners!
In both opah and chi kung master, transmission mechanism is very important. Tuna and a small number of fish, according to the article, have "regional endothermy" (i.e. heat energy is only trapped around the propelling fins), while opah has "whole-body endothermy". In chi kung, the skill of whole body connectedness is of vital important in chi transmission. Master Wang Xiangzai called it "muscles as one" 肌肉如一 . Only with body connectedness can energy be transmitted to other parts of the body effectively, with the source energy coming from the most efficient and strongest muscles.
Another important factor is energy boosting in the transmission process/system. Again this aspect of opah's sophistication is not discussed in the article. In chi kung, it is joint-opening to the extend that the joints become springs that can both trap, transmit energy and boost up energy in the process. Master Wang Xianzai called it "Every part of the body is a spring", which essential means every joint acts as spring to serve the purposes mentioned in the previous sentence. And this is the reason why Song (松) is the most important training concept in tai chi.