Of course humans don't have the full extension/retraction that cats do but our nails do move and we can learn to have control over them. Developing whole body tendon integration is a preliminary stage for learning whole body power. To do this one must practice initiating movement from the nails, the outer periphery of our bodies.
Just like the nails are the ends of the tendons in Chinese Medical theory, the tongue is the end of the muscles.
The chansijin (taijiquan silk reeling power exercises) movements of the head have a little known tongue component. For instance there is a "head forward and back" neck roll that replicates the infant sucking reflex all babies develop. If you do the exercise correctly the whole inside of your throat, including your tongue, will involuntarily come outward and suck back inward with each rolling motion.
The seventh palm change in Baguazhang is sometimes called "snake spits out it's tongue" for the same reason; it is possible to tap into whole body power through activating the sucking reflex in which the tongue goes forward and draws back. With practice, the whole torso will be involved in the movement.
In both of these cases, the tongue remains hidden. This is a type of secret teaching known as "indoor" or "six ears never hear."
Michael Jordan, on the other hand, has not been shy about showing us his tongue. He is by far the greatest Basket Ball player I've every watched.
Now I ask you, is it a coincidence that he also happens to be the only player who constantly sloshed his tongue around in his mouth and regularly stuck it out when he was making full use of his muscles? Was he just fooling around, or was that a secret source of his power?