The lunge is a great lower extremity exercise. Varying the technique helps to target each muscle in a slightly different way; avoiding a plateau in strength gains and keeps your routine interesting.
Keeping your front foot planted, step back into the lunge position. This will challenge your balance and target the posterior chain.
Place your front foot on a foam roller and do a static lunge. The unsteady surface requires extra work for the muscles, especially the inner quads, to keep your knee stable.
Place your back foot on a ball or bench and do a static lunge. This will work the quads and glutes harder on the front foot and stretch the hip flexors on the back leg.
Step forward into a lunge position. At the bottom of your lunge, rotate to the right and left. To progress, hold a weight or a medicine ball.
Step to your side as far as comfortable and squat down. This will help keep the inside part of your thigh flexible and make your glutes work harder.
Step back and across your body into the lunge position. This will target the glutes.
Wrap a band around your knee and tie it so that the band pulls the knee in. As your do your lunge, make sure to keep the knee tracking over top of your ankle.