What is shaft torque
One of the most important factors in selecting the right shaft for your game is the torque of the shaft.
Torque is simply defined as the resistance to twisting that a shaft has during the downswing and impact. The torque value is expressed in degrees, so the lower the degrees of torque, the more resistance the shaft will have to being twisted from the force of the downswing on the club head attached to that shaft. The higher the degrees of torque, the less resistance the shaft will have to being twisted by the mass of the club head on the downswing.
Stronger and faster swing speed players as well as players who pull the club down fast from the top of the backswing will benefit by using a low torque shaft as this will stabilize the club head through impact and give them straighter shots.
Conversely, if you are have slower swing speed and have a very smooth, rhythmic swing without a very aggressive downswing move, you do not want to use shafts with the torque below 3.5 degrees or else the impact feel of the shot can be stiff, and the height of the shot may be too low with less than optimum distance
Anything less than 3.5 degrees is considered low torque, between 3.5 degrees and 5 degrees is mid torque and anything greater than 5 degrees is high torque. Also, the stiffer and heavier the shaft, the lower the torque. As stiff shafts are used by the fast swing players, there is more pressure on the shaft through impact and the tendency to twist is more which may result in the club face opening or closing. A lower torque here will offset the tendency of the shaft to twist and will keep the club face square through impact, resulting is straighter shots.