Hands in pullup grip (pronated), pull the chin over the bar, while also pulling the knees to the chest. This exercise can be done repetitively, or used as an isometric exercise where we hold the chin over the bar, and knees to the chest for a period of time.
Lying on your back (supine) tuck your tailbone, squeezing your legs and glutes tightly. Lift your shoulder blades off the ground by pressing your ribs down and engaging your upper abs. Holding this dish shape, begin to rock front and back. Think of initiating the rock upwards with the legs by pulling the pelvis off the ground, then the upper body rock by pushing the chest forward.
Hanging from a bar, perform a regular grip (pronated) shoulder shrug. At the top of the shrug press forward with your hands into the bar, activating the lat muscles, and reducing the angle between the arms and the body. At the same time, curl up with the abs, bending the knees in an attempt to tap your knees to your elbows. Initiate this movement first with the shoulder press, then add in the leg lift.
Hanging in either a pullup grip (pronated) or chinup grip (supinated), pull until your arms are bent at less than 90 degrees. This movement is isometric, so we will be holding the static position for a length of time. It is important the elbows stay close to the body and not flared out to the sides.
Variations: Pulling until your chin is over the bar, and your elbow angle is compeletely closed, and hold. Or pulling until your elbow angle is 90 degrees and holding in this position.
Seated on the ground with your legs straight and together (piked), put one hand on the ground on either side of your legs. Keeping your back straight lift both legs off the ground repeatedly keeping the legs straight (no knee bend). To increase the challenge walk your hands closer to your knees / feet. To decrease the challenge, put your hands on the ground behind your back so that you are not so closed / piked at the hip.