In order to balance effectively at the middle or tip of the bow, we must use leverage to apply force beyond that supplied by the weight of the bow. To do so, it is necessary to pronate the forearm, as in turning a doorknob to the left. This causes the hand to act as a lever – with the thumb being the fulcrum – and applies the rotational force of the pronating forearm to the bow and string. To use leverage successfully, it is essential to continue to feel the suspension of the arm weight from the shoulder. Too often, cellists misinterpret this action, erroneously lifting the elbow while simultaneously pressing down into the string.
Gerhard Mantel cautions, “If the rotational force of the pronation falls short of matching the vertical force of the arm, the arm will press the frog down to the floor. If the rotational force of the pronation exceeds the vertical force of the arm, the arm will be pushed up.”