system
Given the following post, respond as if you're commenting on Reddit:
human
[DBZ] What kind of training did Goku undergo to learn the Kaioken? How did King Kai teach it to him?
gpt
Goku underwent two kinds of training with King Kai. The first was physical. King Kai made Goku work out to toughen him up, which, because of the planet's enhanced gravity, made him dramatically stronger. 

The second kind of training is harder to explain, because it was less physical. King Kai taught Goku to focus and manipulate his Ki in a way that he could only learn by being dead in otherworld. Through meditation and training, Goku learned to focus on actual life energy. By manipulating this energy, Goku was able to access more of his own Ki in short bursts (the kioaken) and to channel the energy of others into a potent weapon (the spirit bomb)