"popping up" and "Thai massage"

Meaning of "popping up"

In general English, popping up means "to appear suddenly" or "to show up unexpectedly."
In a physical therapy or massage context, it can also describe the "pop" or "click" sound/feeling that comes from joints or soft tissues when stretched or pressed, similar to the sound when cracking knuckles.

Thai massage techniques involve stretching, pressing, and mobilizing the body, which can sometimes cause a popping sensation:

Joint mobilization: A popping sound can happen when gas bubbles inside a joint are released (the same mechanism as knuckle cracking) during your Thai massage session.
Stretching and pressure: Applying deep pressure or stretching certain areas may create a feeling of “release,” sometimes accompanied by a popping sound, which we apply our Thai massage technique to during stretching, combined with the suitable pressure individually.
Psychological relief: For many, this popping sound can feel satisfying and may create a sense of relaxation or "looseness," and you can feel the result after a Thai massage session—more flexibility and looseness from the muscle.