Lunges are considered a unilateral exercise given the workload required of the lead leg compared to the rear. This allows you to better improve asymmetries in strength, compared with squats, for instance. Also, lunges challenge and improve your balance and stability in unilateral movements. The lunge is a great exercise for runners in that the mechanics are similar to running. The step out to landing is similar to the movements of a running stride, but without the large ground reaction force the body experiences when running.