Muscles involved: hamstrings posterior oblique subsystem
 
Form: stand, feet hip width apart, facing cable wall, with attachment clip at the bottom, cuff around one ankle. Brace yourself at the cable wall, shift weight to other leg (which has a slight bend in the knee), brace core, maintain straight back.  Breathe in, and exhale as you slowly pull up the cuffed leg, heel towards gluteals, to 90˚ knee flexion, pause, slowly return foot to ground.
 

Cautions: tubing may be used if cable weights are too heavy. A seated position is also possible.
 
Trainer techniques: cue breathing, cue tall posture with well-aligned spine, and look for motion at the knee. To spot, stand to the client’s side and monitor the angle of flexion and posture throughout.