The lunge and side lunge are very important exercises in many sports, especially when these exercises are executed with Active Cords. The reason for this is that the Active Cords allow you to do the exercises in exactly the same manner as the joint actions occur in many skills.
The lunge is a terrific exercise to develop the ability to take a long stride in a reaching motion as for example in soccer and baseball. It is also a key exercise to develop the feel of the push-off and knee drive as occurs in running. This in turn helps develop a longer stride which is very important for increased speed.
The side lunge is a great exercise to improve cutting actions as needed in football and soccer. It also imitates the joint actions involved when moving out to the side or doing a side shuttle in tennis and other sports.
It is a key exercise for shifting weight forward and developing more power in the weight shift in throwing and hitting actions. Keep in mind that weight shift is the key to transferring your weight onto the front leg which then creates the conditions needed for more powerful hip rotation.
However, in order to get maximum benefit in both the front and side lunges, it is important that you keep the torso erect. Most individuals have a tendency to lean forward as they execute these exercises. Doing this greatly decreases the effectiveness of these exercises.
Not only does the forward lean not duplicate what takes place on the field, but you also do not get a strong stretch of the hip flexors in the lunge and the hip adductors in the side lunge. But this is an important benefit of these exercises.
In addition, by having correct execution of the forward and side lunges, you are able to develop a more powerful push-off. This usually happens after you have developed sufficient strength by doing the exercises at a moderate speed. By changing the speed of execution to an explosive manner you can make the push-off even more powerful.
For more information on these two exercises and their role in many sports see Biomechanics and Kinesiology of Exercise and Explosive Running.