The Baby Get Up
I use the BGU to improve the pattern of trunk flexion and rotation.
I also use it to provide an opportunity to challenge hip and sacro-iliac joint stability in the presence of other body part movements.
The bottom arm moves into internal rotation until it meets it's end-range, at which point the person sits up. The ""screwing home" of the shoulder creates a stable joint. As the person continues to press the hand down to the floor, the shoulder girdle is brought with it, pushing the trunk off the ground. Actively sit up.
Place the top hand against the "up" leg. As you sit up, keep the hand/arm against the inside of the knee.
The top leg, remaining in active abduction and external rotation, creates hip and sacro-iliac joint stability.
The three stable areas, bottom arm, bottom hip/hemipelvis and top hip/hemipelvis, provide a stable base for the trunk to flex and rotate around.
In other words, activating stabilisers permits expression of mobilisers.
Top leg collapses; bottom arm loses connection with the ground; jerky trunk flexion and rotation; bottom leg loses extended position.