Which of the following muscles is categorized as primarily phasic?

The rhomboids are classified as primarily phasic muscles, which means they are more involved in dynamic movements and are typically activated with motion. Phasic muscles are often responsible for sustaining function through movement, and they tend to be more responsive to quick or repetitive actions.

The rhomboids play a crucial role in retracting the scapula and stabilizing the shoulder girdle during various upper body activities. When engaging in overhead movements or activities that require pulling, these muscles actively contract to maintain appropriate scapular positioning.

In contrast, the transversus abdominis is a postural muscle that primarily stabilizes the core and acts as a stabilizer rather than a mover. The rectus abdominis, while it does participate in dynamic movements, is often considered more tonic because it maintains posture and stability for the trunk. The quadratus lumborum is also more of a postural muscle as it helps with lateral trunk stability and movement. Thus, in recognizing the role and function of these muscles, the rhomboids fittingly fall into the phasic category due to their involvement in movement dynamics rather than stabilization.