The golf shaft is a spring. Depending on the stiffness of that spring it takes a certain amount of time for the spring to recover from the deflected position to the neutral position (for the golf shaft, straight). It is at this neutral position that the golf shaft reaches its greatest effectiveness (maximum speed and club face square). What does this curve above show? First it shows the variation of the energy or load in the shaft at any given time as the shaft cycles while it vibrates. The Peak Load is achieved during the players down swing as they accelerate the club head up to speed. Once the Load on the shaft starts to drop off the spring action of the shaft takes over to return the shaft to straight and what should be ball impact. The timing problem involved in this sequence is to find the right natural frequency for the players club that will return the shaft to straight during the players unique time between peak load and the point of ball impact. This time is represented by 1/4 of a cycle of the clubs natural frequency as shown in the curve above.