This exercise increases the strength of the abdominals (oblique muscles) that generate rotational force. It also helps coordinate the torso and arm movements, therefore reducing the likelihood of overuse of just the arms during the swing.
It's important that the arms and body work together in the golf swing, to generate power and to gain consistent ball-striking.
Maintain a slight deep abdominal contraction by drawing your belly button in towards your spine throughout the exercise.
Check out more from Jon Bowskill, TG's fitness guru, at: www.jonbowskill.com.