This exercise is excellent for improving ankle stability and hip strengthening! This is really a series of 3 lunges using a slider, hence the name lunge series. This is composed of a side lunge, posterior lunge, and posterolateral (or curtsy) lunge. Here are the key concepts with each lunge: 1) Keep control of your knee and make sure it stays in line with your first two toes. Do not allow the knee to valgus, or drop to the inside, since this will increase stress to the knee and may cause pain. 2) Control your trunk and keep the chest upright throughout the movement. Avoid leaning too far forward and bending through the low back. 3) Reach as far as you can with the foot on the slider while controlling the movement. Keep your heel down and foot flat on the stance leg. These lunges are great for athletes especially soccer, hockey and football players! Give it a try and let me know what you think!