Jackknife
Classical inversion: the hips roll up and over the head into a shoulder stand, then the legs lower over the head — spinal articulation, hamstring length, and shoulder stability.
- Body
- Reformer
- Movement
Teaching Precautions
Common precautions, not exhaustive. Screen every client and refer when in doubt.
- Neck & Cervical Strain: Inversion loads the cervical spine; keep the head supported and skip if there is any neck compromise.
- Osteoporosis / Osteopenia: Loaded flexion and inversion; substitute neutral or extension-based work.
- Pregnancy: Supine work after the first trimester can compress the vena cava; elevate the head and shoulders or use a side-lying alternative.
Apparatus Setup
Reformer
Target Muscles
Setup Instructions
Lie supine on the carriage with the legs extended toward the ceiling, arms long by the sides with the hands pressing the carriage.
Execution Instructions
Exhale to roll the hips up and over the head into a shoulder stand with the legs stacked over the hips, then lower the legs toward the floor behind the head; inhale to return with control.
Teaching Cues
"Peel the hips up and over the head — the spine articulates, it does not jump."
"Stack the hips over the shoulders and keep the legs long."
"Exhale to lift over, inhale to lower with control."
Modifications & Progressions
Bent Knee Lift (Regression)
Bend the knees to shorten the lever and reduce the hamstring demand.
Extended Hold (Progression)
Hold the shoulder stand for two breaths before lowering.
No Inversion (Injury Modification)
For neck strain, keep the hips low with the head supported and substitute a bent-knee roll-up that never takes the legs overhead.
Similar Exercises
Same category, or body position when the category is unique.