Isometric contraction is tension.
Tension is a vital part of any gymnasts conditioning program.
Gymnast A stands with a slouching body and muscles looking soft. Gymnast B stands erect with abdominal and gluteal muscles contracted but no significant change in body shape is made. This posture is desirable for a gymnast. Gymnast B has more chance of doing a handstand like this. The abdominals must be strong, so first teach the sit-up.