How to Do Jack Knives

Jack Knives is a core exercise using bodyweight, listed as beginner in the A90 Training Club catalogue.

Primary muscle

Core

Equipment

Bodyweight

Difficulty

Beginner

01 / Move with control

How to perform

How to do Jack Knives

  1. 01Lie flat on your back with arms extended overhead and legs straight.
  2. 02Exhale as you simultaneously lift your torso and legs to form a V shape.
  3. 03Reach your hands toward your shins or toes at the peak of the movement.
  4. 04Inhale as you lower back down with control without letting your heels touch the floor.

Same guidance shown inside the A90 app

02 / Anatomy

Muscles worked by Jack Knives

Primary Stabiliser Inactive

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Primary movers

  • Core Stabilises the spine and transfers force.

Stabilisers

  • Lower back Stabilises the spine during lifts and bends.
  • Forearms Grips and stabilises the wrist under load.

03 / A90 Coach

A90 Coach tip

Drive your lower back into the floor throughout the movement to prevent the hip flexors from taking over the load.

Same coaching engine used inside the A90 app

05 / FAQ

Jack Knives questions

What muscles does Jack Knives work?

Jack Knives is catalogued as a core exercise in A90 Training Club, with the core as its primary muscle group.

How do you do Jack Knives correctly?

Lie flat on your back with arms extended overhead and legs straight. Exhale as you simultaneously lift your torso and legs to form a V shape. Reach your hands toward your shins or toes at the peak of the movement. Inhale as you lower back down with control without letting your heels touch the floor.

What is the A90 coach tip for Jack Knives?

Drive your lower back into the floor throughout the movement to prevent the hip flexors from taking over the load.

Is Jack Knives suitable for beginners?

Jack Knives is rated beginner in the A90 Training Club catalogue.

Do you need equipment for Jack Knives?

No. Jack Knives is listed as a bodyweight movement in the A90 catalogue, so you can train it with no kit.

A90 Intelligence

Put this into a real plan.

A90 Intelligence programmes jack knives into a 30, 60 or 90 day plan built around your equipment, then adjusts it as you train.

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