Bicycle Crunch Joint Actions. Repeat until the set is complete. Torso flexion and vertebral flexion are mean the same thing.
Torso flexion and vertebral flexion are mean the same thing. The rectus abdominis attaches to the ribs and pelvis and crosses over the front of the abdomen. Bring one knee and the opposing elbow close to each other by crunching to one side and fully extend the other leg.
Then through contracting the abdominals raise the right shoulders from the ground and crunch across to tap the left knee with the right elbow or as close as you can.
Repeat until the set is complete. Once at the top rom hold for one second maximally contract the abdominals and slowly lower to the floor again. Basically multiple muscles work in unison to perform a movement. Agonist or prime mover is the rectus abdominus muscle.