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Straight Leg Sit-Up

Step by step instructions, muscle activation and variants for the Straight Leg Sit-Up.

EasyAbsCore

About this exercise

The Straight Leg Sit-Up is a classic abdominal exercise performed with the legs fully extended, which increases the lever arm and places greater demand on the hip flexors and abs compared to a bent-knee sit-up. Keeping the legs flat challenges the core to stabilise against the additional load. It is suitable for developing abdominal strength and endurance.

How to Perform

  • Lie on your back with your legs fully extended and your arms crossed over your chest or placed behind your head
  • Press your lower back lightly into the floor to engage your core
  • Exhale and slowly curl your upper body upward, bringing your torso toward your thighs
  • Rise until your torso is near vertical or as far as your flexibility allows
  • Hold briefly at the top, then inhale and slowly lower back to the floor
  • Repeat for the desired number of repetitions

Muscle Activation

Primary
AbsCore
Secondary
QuadricepsObliquesOuter thighs

About the Straight Leg Sit-Up

The Straight Leg Sit-Up is a foundational movement that builds strength and muscle through controlled, progressive overload. Train it 1 to 2 times per week with 3 to 5 working sets per session, gradually adding weight or reps as form holds up.

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