Lisa demonstrates 3 GHD movements:
1. GHD Situp: Core stays engaged from the upper abs through the hip flexors
2. GHD Hip extension: The back stays flat and the hip movement is stabilized through the Glutes and the Hamstrings.
3. GHD Back extension: The hips stay static and are stabilized with the Glutes and the Hamstrings, but the Cervical/Thoracic/Lumbar spine goes through a carefully controlled flexion-extension movement pattern.