Lie flat on your back with your legs straight and your arms extended overhead, keeping them just off the floor.
In one fluid motion, simultaneously lift your legs and torso, reaching your hands towards your toes. Your body should form a "V" shape at the top.
With control, slowly lower your legs and torso back to the starting position.
Tips
Initiate the movement by lifting your legs and torso at the same time rather than leading with one before the other, so that both arrive at the top of the V simultaneously.
Lower your legs and torso slowly and with control on the way down, keeping them just off the floor at the bottom rather than letting them drop and rest.
Keep your legs as straight as your hamstring flexibility allows throughout the movement, bending the knees only as much as necessary to complete the range.
Common mistakes
Leading with the upper body while the legs lag behind produces an uneven crunch rather than a true V shape at the top.
Bending the knees sharply to make the reach easier shortens the lever and reduces the range of motion the exercise is intended to train.
Make Every Set Count.
Plan your workouts, track every session, and see your progress over time.