Stand with your core braced and a flat back, holding a pair of dumbbells in each hand. This is your start position. Take a big step forward with your left leg and bend at the knee, slowly lowering your body until your front knee is bent at least 90 degrees, whilst your rear knee should be hovering just off the floor. Lean your torso forward as you do so to increase hip flexion. Pause at the bottom of the movement, then extend your knee as you push off from your back foot to move forwards into a lunge position with the other leg. Keep the forward lean in your torso throughout and focus on lunging forwards not up and down. Continue to alternate legs until all the required reps (or time) are completed.