Which exercise demonstrates the movement in the sagittal plane?

The forward lunge is the exercise that demonstrates movement in the sagittal plane. The sagittal plane divides the body into left and right halves and is characterized by movements that occur forward and backward. In a forward lunge, one leg steps forward while the other leg remains behind, effectively moving the body in a forward direction. This action emphasizes the flexion and extension of the knee and hip joints, which are key movements within the sagittal plane.

In contrast, the other exercises either involve movements predominantly in different planes or focus on lateral and vertical movements. For instance, a pull-up and cable lat pull-down primarily work in the vertical plane through pulling motions, while the side raise involves lateral movements, characteristic of the frontal plane. Therefore, the forward lunge clearly exemplifies the sagittal plane movement, making it the appropriate choice.