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.