The phrase "the king of all exercises" is a colloquial expression used to describe an exercise that is considered to be the most effective or beneficial among various options. Full definition
The first on our list of ball - busting finishers is the king of exercises, of course. (fitnessandpower.com)
Even though it competes shoulder to shoulder for the title «the king of exercises» with the squat, I would put my bets on the deadlift simply because it's badder, meaner, more hardcore and it targets more muscle mass than the squat. (fitnessandpower.com)
Squats are called by many the «king of exercises» along with the deadlift as there isn't a muscle on the body that it's not worked by these two. (fitnessandpower.com)