Jackknife Sit-Up

What it is

This dynamic core exercise involves simultaneously raising your extended arms and legs to meet in the middle. It effectively strengthens and sculpts your abdominal muscles. You perform this movement using only your body weight.

Technique tips

• Engage your core muscles from start to finish.
• Exhale smoothly as your hands and feet meet.
• Keep your legs extended, lifting to about 35-45 degrees.
• Lower your body with control, avoiding any sudden drops.
• Ensure your upper torso lifts completely off the floor.

How to track your progress

Log reps, and add the extra load if you wear a belt or a vest. Straddly counts your bodyweight in the estimated max, so added weight and extra reps both show up as progress, and new records are flagged during the session.