Suspension Jack Knife
Suspension Jack Knife Exercise Description
The Suspension Jack Knife is a knee‑tuck performed with your feet in suspension straps and your hands on the floor in a high plank. It primarily challenges the anterior core to resist lumbar extension while the hips and knees actively flex to draw the knees toward the chest. Key musculature includes the rectus abdominis and external/internal obliques for trunk stabilization, the hip flexors (iliopsoas and rectus femoris) for the tuck, and the serratus anterior, shoulders, and triceps to maintain a stable shoulder girdle. The goal is a controlled knee‑to‑chest motion without letting the low back sag or the shoulders drift behind the wrists. Expect strong demands on balance and body control due to the moving straps and long lever of the plank position.
- Muscle Groups: Abs, Core, Waist
- Target Muscles: Rectus Abdominis
- Assisting Muscles: External Obliques, Internal Obliques
- Stabilizing Muscles: Serratus Anterior, Triceps Brachii - Long Head
- Body Area: Upper Body
- Body Parts: Core, Torso
- Body Surface: Front
- Body Symmetry: Bilateral
- Equipment: TRX Bands
- Exercise Patterns: Other
- Exercise Type: Strength, Suspension
- Functional Grouping: Trunk Flexors
- Joint Involvement: Multi-joint
- Muscle Location: Stomach
- Movement Direction: Horizontal
- Muscle Position: Anterior
- Gender: Female
How To Do The Suspension Jack Knife Exercise
‘- Set suspension straps so foot cradles are roughly mid‑calf height. Face away from the anchor, kneel, and place the tops of your feet (laces down) into the cradles.
– Place hands on the floor under shoulders and step out to a high plank: arms straight, shoulders stacked over wrists, body in a straight line from head to heels.
– Create tension: press the floor away, slightly protract the shoulder blades, draw ribs down, and lightly brace glutes to keep a neutral spine.
– Without shifting shoulders behind wrists, smoothly flex hips and knees to draw both knees toward your chest, letting the straps glide forward.
– Keep pelvis level; avoid hiking or sagging the hips and avoid rounding through the upper back.
– Pause briefly with knees under hips while maintaining trunk stiffness and even pressure through both hands.
– Reverse the motion by extending hips and knees to return to the strong plank, controlling the straps to prevent swinging.
– Breathe throughout; do not hold your breath. Stop the set if you lose plank alignment or shoulder position.
Suspension Jack Knife Tips
‘- Set the suspension straps so the foot cradles are about mid‑calf height before starting.
– Place the tops of your feet in the cradles with laces facing down to secure your footing.
– In the plank, stack your shoulders directly over your wrists and keep your body in a straight line from head to heels.
– Press the floor away and slightly protract your shoulder blades to create upper‑body tension.
– Draw your ribs down and lightly brace your glutes to help maintain a neutral spine.
– As you tuck, flex your hips and knees to draw your knees smoothly toward your chest without letting your shoulders drift behind your wrists.
– Keep your pelvis level during the movement, avoiding both hip hiking and hip sagging.
– Avoid rounding through your upper back as you bring your knees under your hips.
– Control the return to plank by extending hips and knees smoothly, limiting any swinging of the straps.
– Breathe continuously during the set and stop if you lose your plank alignment or shoulder position.
Suspension Jack Knife Beginner Introduction
The Suspension Jack Knife is a suspension‑strap core exercise that blends a long‑lever plank with a smooth knee‑tuck. With the feet supported in moving straps and the hands grounded, the body hovers in a straight, horizontal position while the knees travel in toward the torso. This combination challenges the abs and side abs to keep the midsection from arching, even as the hips and knees bend to bring the legs forward.
Because the straps can sway, the move places extra demand on balance, coordination, and shoulder stability. The hip flexors and front thighs drive the tuck, while the chest, shoulders, and arms support the upper body and help hold a strong plank shape. Throughout the motion, the aim is steady control—rather than speed—so the torso stays firm, the lower back feels supported, and the straps glide back and forth without wild swinging. This makes the exercise a demanding option for building total‑body tension and core strength using suspension equipment.