Benefits of the lunge exercise include developing strength and firmness in your lower body. The twisting part of the exercise teaches you to rotate over the resistance of your lower body just like what you need to do in the golf swing.

Hold a golf club parallel to the ground and extend your arms out in front of you.
Lunge forward with your right leg, keeping your arms parallel to the ground.
As you lunge forward, simultaneously rotate your torso to the right, keeping your arms parallel to the ground, hold position for a moment.
Then rotate your torso to the opposite side and again hold position for a moment.
Return to the start position and repeat on the opposite leg.
Do 8 to 10 repetitions on each leg.