Training is the practice of applying a stimulus to adapt, then recovering from it.
The stimulus is some type of work or resistance. Resistance can be modified (increased or decreased) by use of load, leverage, momentum, and range of motion.
Gymnastics is the art of modifying all of these except load. The load is your bodyweight. The result is measured in strength-to-bodyweight ratio.
Gymnastics is second to none in developing strength:bodyweight ratio.