Which of the following exercises focuses on horizontal arm movement?

The exercise that focuses on horizontal arm movement is the T Raise. This exercise involves extending the arms out to the sides, creating a "T" shape with the body. By doing so, it effectively targets the muscles associated with shoulder stability and upper back strength, promoting proper posture and functional movement.

In contrast, the I Raise involves raising the arms straight up overhead, targeting the upper traps and shoulder muscles but not focusing on horizontal movement. The W Raise incorporates a more diagonal arm movement, creating a "W" shape with the arms that emphasizes activation of different muscle groups and shoulder mechanics. The L Raise is performed at a right angle and primarily works on the shoulder muscles while keeping the arms in a more vertical position.

Hence, the T Raise is specifically designed for horizontal arm movement, making it the correct choice for this question.