Suspension Twisting Jack knife
- Target muscle
- Obliques
- Synergist muscles
- Iliopsoas, Tensor Fasciae Latae
- Equipment
- Suspension
- Body part
- Waist
- Type
- Strength
The Suspension Twisting Jack knife is a core strength exercise that primarily targets the obliques, with the iliopsoas and tensor fasciae latae driving the hip-flexion pull. Performed in a suspended plank with your feet in the straps, it combines rotational waist flexion with hip-flexor engagement, making it an effective choice for building rotational core strength and stability.
How to do the Suspension Twisting Jack knife
- 1Set the suspension straps to mid-calf height with the anchor point behind you, then kneel and place the tops of both feet securely in the foot cradles.
- 2Walk your hands forward until your body forms a straight plank from heels to head, with your hands directly under your shoulders and arms fully extended.
- 3Brace your core firmly, squeeze your glutes, and keep your hips level — this is your starting position.
- 4Exhale and drive both knees toward your right elbow, rotating through your waist so your hips twist to the right.
- 5Pause for a brief moment at the top with your obliques fully contracted.
- 6Slowly extend your legs back to the plank position under control, keeping your hips from dropping or rising.
- 7Drive both knees toward your left elbow on the next rep, again rotating through the waist.
- 8Continue alternating sides for the target number of reps, then carefully lower your knees to the floor and remove your feet from the straps to finish.
Form tips
- Initiate the movement from your waist, not your shoulders — the rotation should come from the torso twisting, not from pulling with your arms.
- Keep your hips at the same height as your shoulders throughout; sagging or piking shifts load away from the obliques and onto the lower back.
- Control the return phase — let the straps pull your legs back slowly rather than swinging them, which keeps tension on the muscles.
- The further your hands are from the anchor point, the greater the instability and the harder the exercise; start closer if you are new to suspension training.
Common mistakes
- Letting the hips sag toward the floor on the return phase, which transfers stress to the lumbar spine and removes oblique tension.
- Piking the hips upward as the knees come in, which makes the movement a hip hinge rather than a rotational crunch and reduces oblique activation.
- Rotating from the shoulders instead of the waist, which bypasses the obliques and lets the upper body do work the core should be doing.
- Swinging the legs back uncontrolled to gain momentum, reducing time under tension and increasing the risk of losing balance in the straps.
- Holding your breath throughout the set, which raises intra-abdominal pressure unnecessarily — exhale as you pull your knees in and inhale on the return.
Frequently asked questions
What muscles does the Suspension Twisting Jack knife work?
It primarily targets the obliques, which control the rotational crunch. The iliopsoas and tensor fasciae latae act as synergists, driving the hip flexion that pulls the knees toward each elbow.
How high should I set the suspension straps?
Mid-calf height is standard — it places your body at a challenging angle while keeping you close enough to the floor to bail safely. Lowering the straps increases difficulty; raising them makes it easier.
Is the Suspension Twisting Jack knife suitable for beginners?
It is better suited to intermediate exercisers who can already hold a solid plank for 30–60 seconds and have some experience with suspension training. Beginners should first build plank endurance and practice a standard suspension jack knife before adding the twist.
How many sets and reps should I do?
For core strength, 3 sets of 8–12 reps per side works well. Count each side separately and alternate with each rep to keep the work balanced across both obliques.
Where should I feel this exercise?
You should feel the main work in the sides of your waist (obliques) as you rotate and crunch the knees in. A secondary pulling sensation in the front of the hips (iliopsoas and tensor fasciae latae) is normal and expected.
