According to J. Pilates, true flexibility can be achieved only when:

True flexibility, according to J. Pilates, is achieved when all muscles are uniformly developed. This concept highlights the importance of balance in muscle strength and coordination throughout the body. When muscles are uniformly developed, there is reduced tension in the musculature, which allows for a greater range of motion in the joints. Uniform muscle development means that no single muscle group is overpowering another, leading to enhanced postural alignment and stability. This balance is essential for performing movements with grace and efficiency, which ultimately contributes to overall flexibility.

Achieving flexibility through the lens of uniform muscle development aligns with the principles of Pilates, emphasizing a holistic approach to movement. This approach contrasts with the notion that flexibility can be solely gained through relaxation, prioritization of stretching, or performing quick movements, as those factors alone do not ensure the balanced strength required for true flexibility.