90-Degree Single Knee Crunch

1. Start by lying on your back on a comfortable surface with your knees bent at 90 degrees, so your thighs are perpendicular to the floor and your calves are parallel to the floor.

2. Place your hands lightly behind your head without interlocking your fingers. Make sure not to pull on your neck during the exercise.

3. Engage your core muscles by drawing your belly button towards your spine.

4. Slowly crunch up by raising your head, neck, and shoulder blades off the ground. As you crunch up, simultaneously bring one knee closer to your chest by lifting your hip slightly off the ground.

5. Pause at the top of the crunch and hold the contraction in your abs for a moment.

6. Slowly lower your upper body back down to the starting position while also returning your knee to the 90-degree starting position.

7. Repeat the movement with your other knee, alternating sides with each rep.

8. Keep the movement controlled and focused on using your abdominal muscles rather than gaining momentum from the hips or neck.

9. Continue alternating sides for the desired number of repetitions and sets.

Be sure to maintain good form throughout the exercise, keeping the movement smooth and controlled to maximize engagement of the abdominal muscles and avoid strain on the neck and lower back.

---