Suspended Jack-knife
The Suspended Jack-knife primarily works the Rectus Abdominis, with secondary activation of the Adductor Brevis, Adductor Longus, External Obliques, Iliopsoas, Pectineus, Sartorius, Tensor Fasciae Latae and stabilizer support from the Anterior Deltoid, Brachialis, Erector Spinae, Pectoralis Major (Sternal), Rectus Femoris, Rhomboids, Serratus Anterior, Trapezius (Lower), Trapezius (Middle), Triceps (Long Head). It is a suspension compound exercise at intermediate difficulty.
The Suspended Jack-knife is a intermediate compound exercise performed with suspension, following a flexion movement pattern. It primarily targets the Rectus Abdominis, with secondary engagement of the Adductor Brevis, Adductor Longus, External Obliques, Iliopsoas, Pectineus, Sartorius, Tensor Fasciae Latae. This is a bilateral pulling movement, engaging both sides of the body simultaneously.
A suspension compound pull exercise targeting the Rectus Abdominis.
| Equipment | Suspension |
|---|---|
| Difficulty | Intermediate |
| Type | Compound |
| Movement | Flexion |
| Force | Pull |
| Laterality | Bilateral |
| Primary | Rectus Abdominis |
| Secondary | Adductor Brevis, Adductor Longus, External Obliques, Iliopsoas, Pectineus, Sartorius, Tensor Fasciae Latae |
Muscles Worked
The Rectus Abdominis is the primary mover, taking on the bulk of the workload throughout the full range of motion. The Adductor Brevis, Adductor Longus, External Obliques, Iliopsoas, Pectineus, Sartorius, and Tensor Fasciae Latae act as secondary movers, assisting the primary muscles and contributing meaningfully to the overall output. The Anterior Deltoid, Brachialis, Erector Spinae, and 7 other muscles act as stabilizers, maintaining joint position and postural alignment throughout the movement.
Primary Muscles
- Primary Muscle Rectus Abdominis (core)
Secondary Muscles
- Secondary Muscle Adductor Brevis (adductors)
- Secondary Muscle Adductor Longus (adductors)
- Secondary Muscle External Obliques (core)
- Secondary Muscle Iliopsoas (hip_flexors)
- Secondary Muscle Pectineus (adductors)
- Secondary Muscle Sartorius (hip_flexors)
- Secondary Muscle Tensor Fasciae Latae (hip_flexors)
Stabilizer Muscles
- Stabilizer Muscle Anterior Deltoid (shoulders)
- Stabilizer Muscle Brachialis (biceps)
- Stabilizer Muscle Erector Spinae (back)
- Stabilizer Muscle Pectoralis Major (Sternal) (chest)
- Stabilizer Muscle Rectus Femoris (quadriceps)
- Stabilizer Muscle Rhomboids (back)
- Stabilizer Muscle Serratus Anterior (chest)
- Stabilizer Muscle Trapezius (Lower) (back)
- Stabilizer Muscle Trapezius (Middle) (back)
- Stabilizer Muscle Triceps (Long Head) (triceps)
How to Perform
Preparation
- Sit on floor facing suspension trainer loops in low position.
- Place right foot in left lower loop.
- Cross left leg over right leg placed in right lower loop.
- Turn body to right and place hands on floor, shoulder width apart.
- Turn body to kneel on hands and knees.
- Reposition hands squared with desired distance from suspension trainer, shoulder width or slightly wider.
- With arms straight, raise knees from ground so body is supported by arms and suspension trainer.
Execution
- Pull legs under torso by bending hips and knees.
- Pull knees toward chest hips and knees until completely flexed.
- Return by extending hips and knees to original position.
- Repeat.
Comments
- SeeSuspended Prone Feet Mount/Dismount.
- Keep shins close to horizontal and arms straight with shoulders positioned above hands.
- Dismount by removing straps while kneeling or after sitting on one side of hip before rotating body to seated position.
Tips & Common Mistakes
- Control the eccentric phase — the lowering portion drives significant muscle development.
- Avoid momentum; focus on feeling the target muscle work through the full range.
- Full range at both ends maximizes stretch at the bottom and contraction at the top.
Programming Suggestions
Adapt your sets and reps to your training goal.
| Strength | 3–5 sets × 3–6 reps at 80–90% 1RM with 2–4 minutes rest. |
|---|---|
| Hypertrophy | 3–5 sets × 6–12 reps at 65–80% 1RM with 60–120 seconds rest. |
| Endurance | 2–4 sets × 15–20 reps at 50–65% 1RM with 30–60 seconds rest. |
Alternative Exercises
These exercises target the same primary muscles (Rectus Abdominis) and can be substituted based on your equipment or variation preferences.
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