Can't Do a Pullup? Try This Lying Down Modified Pullup!
The purpose of this movement is for those who do not have access to a pull up bar or perhaps cannot do a pull up. It is designed to utilize just your bodyweight in having a similar effect. You can use the lying modified pull up to build strength to try an assisted pull up and then a pull up.
Perform this movement by lying flat on your back with your feet on the floor, knees above you and your elbows at 45 degree angles from your torso. Your shoulders should be down and press back against the floor.
You will engage your scapula or shoulder blades by squeezing your shoulders down towards your hips and squeezing your shoulders back together. This should puff out your chest. While doing this, you will drive your elbows into the ground.
If you have enough strength, then your torso will raise up off the ground. It will also hyper engage your abs, but also your rear delts, upper back muscles and lats. These are the same exact muscles used in a pull up.
Keep your core tight and flexed the entire time. When you reach about a 45 degree angle with your back of the floor, lower yourself back towards the ground while maintaining tension throughout your body. Lower your body until the back of your arms are laying against the ground again, then drive yourself back up in the same way.