This exercise involves lying on your back with your legs straight and lifting your upper body and legs off the ground simultaneously, reaching your hands towards your toes. It targets the abs, lower back, and hip flexors.

Muscle Group

Equipment Required

Jackknife Instructions

  1. Stand with your feet shoulder-width apart and your arms at your sides.
  2. Jump up and bring your knees to your chest while simultaneously bringing your arms up and over your head.
  3. Land softly on the balls of your feet with your knees slightly bent and your arms back at your sides.
  4. Repeat the jump and tuck motion for the desired number of repetitions.

Jackknife Form & Visual


Jackknife Benefits

  • Increases cardiovascular endurance
  • Improves lower body strength and power
  • Engages multiple muscle groups, including quads, glutes, hamstrings, calves, and core
  • Improves balance and coordination
  • Burns calories and aids in weight loss
  • Can be modified for different fitness levels

Jackknife Muscles Worked

  • Rectus abdominis
  • Obliques
  • Hip flexors

Jackknife Variations & Alternatives

  • Jackknife sit-up
  • Jackknife push-up
  • Jackknife crunch
  • Jackknife plank
  • Jackknife twist