Jackknife

Teaching points

• Kneel on your hands and knees, resting your shins and ankles on the ball
  
  
• Push the ball back to lift and straighten your knees
  
  
• Your body should now be in a straight line from shoulders to feet
  
  
• Slowly reverse the movement to bring the ball back in and your knees directly under your hips
  
  
• Keep your back flat and the stomach pulled in throughout

Variations and progressions

• This is a more advanced version of the reverse plank exercise

Muscles worked

• Rectus abdominus
  
  
• Transversus abdominus
  
  
• Erector spinae

Alternative exercises

• Reverse plank on a swiss ball
  
  
• Plank on a swiss ball
  
  
• Plank
  
  
• Side plank

Related injuries

• Abdominal strain