The three-way lunge may seem like a cheat, given that it's three different movements in a single exercise, but it's a damn good exercise for hitting your abductors and adductors in addition to your quads, hamstrings, and glutes. Using a weighted barbell (start with a light weight to get used to the exercise), you'll perform a front lunge, side lunge, and curtsy lunge in succession, always leading with the same leg, before repeating all four moves for the full set before switching legs. Trust me, your lower body will burn.
Stand tall, your feet roughly shoulder-width apart, holding a lightweight barbell across the back of your shoulders. If you don't have access to a barbell, you can simply do the exercise while holding a set of dumbbells at your sides, or without weights in a pinch.
Take a step forward with your right foot, planting your heel, allowing your left heel to come off the ground. Keeping your torso tall, bend both knees and lower your back knee toward the ground. Make sure your right knee is tracking in alignment with your toes. Just before your left knee touches down, press through your front heel and push yourself back to the starting position.
Immediately transition to a side lunge by taking a wide step laterally with your right foot. Keep your left leg straight, and press your hips back while bending your right knee, lowering your glutes toward the ground. When you've lowered your glutes as far as you can while keeping your right knee aligned with your toes, press through your heel and return to the starting position.
Now transition to a curtsy lunge by stepping your right foot diagonally behind your left foot, as if you were curtsying, planting the ball of your right foot on the ground. Keeping your knees aligned with your toes throughout this movement with your torso erect, bend both knees and lower your back knee toward the floor. Just before it touches down, reverse the movement and press through your left heel to return to the starting position.
This front lunge, side lunge, curtsy lunge pattern counts as a single repetition. Perform six to eight total reps before switching legs. Complete two sets per leg.