Final answer:
To strengthen the quadratus lumborum muscle, which is vital for posture and stability, the recommended exercise is active resisted lateral flexion of the torso.
Step-by-step explanation:
The quadratus lumborum is a muscle of the posterior abdominal wall that plays a critical role in stabilizing the body and maintaining posture. It is specifically responsible for the lateral flexion of the torso, which is the bending of the neck or body toward the right or left side. To strengthen it, it is recommended to perform movements that require active resistance in lateral flexion.
Active resisted lateral flexion exercises would involve the client moving their torso to the side against resistance, which could be in the form of weights, resistance bands, or manual pressure applied by a trainer. By performing these exercises, the quadratus lumborum is engaged and strengthened, leading to improved core stability and support for the lumbar spine.
The final answer to the question of which movement should be performed to strengthen the quadratus lumborum muscle is lateral flexion of the torso. Active resisted lateral flexion exercises will engage and strengthen this postural muscle optimally.