Step 1: Begin with the TRX straps in the lowest point, a few inches above the ground. Place your feet in the straps so the tops of your feet are facing down. Face away from the anchor point.
Step 2: Place yourself into a strong plank position, keeping your feet in the straps. moving further away from the anchor point makes the exercise more challenging.
Step 3: While holding the strong plank position, alternate a knee-to-chest movement, focusing on pulling with the abdominal muscles. When one knee is being brought to the chest, the other leg is returning to the starting plank position.
Step 4: Repeat this movement several times.
How to progress the exercise
The progression of this exercise is all about levers. The shorter the lever (as in the knees to chest), the easier the movement is. If you perform the exercise with your legs straight (ie: pike), the challenge is much greater.
Tip: Mastery of a strong plank is needed for this exercise, especially to avoid sagging at the hipe when performing the exercise very dynamically. The abdominal muscles need to be firing quite strongly to avoid overusing the hip flexors in the knee to chest movement.