A good conditioning for flexibility requires long times, constancy, commitment and remarkable patience, for this reason, many aspiring practitioners tend to underestimate (if not even avoid) these kinds of activity.
As we have already said, a flexible body offers however crucial advantages in terms of combat aptitude:
Increased resistance to joint levers (arms, etc.)
Greater elasticity and therefore resistance to direct and indirect damage (falls, etc.)
Greater power and speed (the movements do not undergo the passive brake of limited mobility)
Greater amplitude of movement and technique (head kick, etc.)
More performance during stiffening (when we are exhausted by the forces, having better tendons gives us a further margin of operativity)
In some cases shorter recovery times (eg. after a slight injury)
In 6DKF, good body elasticity / flexibility must respond to very stringent parameters, dictated by the inevitable need for application outside predetermined contexts.
Conditioning must be so much more than we choose to use in combat
Performance must be at our disposal even in the absence of heating (eg. after a surprise attack)
Flexibility must also be able to operate / resist under any force coming from any direction (opposite, lateral, etc.)
Flexibility must be dynamically accessible from any position (in flight, in ground combat, etc.)
Flexibility must be instantly and instinctively available (no preparations, no breathing, no relaxation, no concentration, etc.)
To achieve this kind of results, we need what (at the dawn of the Shaolin Temple) Bodhidharma called the gradual "mutation of the tendons".
This is a work of breathing, relaxation and advanced body control through the right Yoga, Qi Gong, power stretching (etc.) exercises (we will all see them all).