While performing the overhead squat assessment, the personal trainer observes a client demonstrating a low back arch movement dysfunction. Which of the following muscles is probably overactive?

- Latissimus dorsi.

Explanation:

As per the question, 'Latissimus dorsi' is the muscle that is probably overactive that has lead the patient to suffer back arch movement dysfunction. This dysfunction has made him unable to move his back and find discomfort to perform the overhead squat (as observed and assessed by the instructor) due to the excessive back pain. The clients muscle 'Latissimus dorsi' would have become overactive due to spending long hours of seated position (placing hip-flexors in a compressed position) that evokes such dysfunction and inability to perform these exercises due to overactive Latissimus dorsi.