Trunk Stability

Maintaining the towel between the knees keeps the lower body actively engaged throughout the movement. The Copenhagen position activates the side-plank stabilizers alongside the adductors. The dual-contact setup — towel in hand and between the knees — promotes midline stability. The upper body and torso should stay steady during the exercise. During each exhale reach, the trunk should not move. A stable trunk should be maintained throughout mountain climbers. During the movement, only the legs should move from the stable push-up position. The drill specifically requires avoiding rotation, shifting, or other trunk movement during the reach. The exercise trains frontal-plane trunk control as one of its primary functions. Maintaining a stable trunk position is the main goal of the drill. The trunk must remain in the side-plank position throughout the arm rotation.