Unilateral

Unilateral refers to "one side." It is a term used to describe movements or structures on one side of the body. For example, when the erector spinae contract unilaterally, they contribute to ipsilateral flexion and ipsilateral rotation.

For more examples of bilateral used in anatomy (including a video lecture), check out:

• Lesson 1: Anatomical Position and Anatomical Directions
• Lesson 3: Joint Actions
• Lesson 18: The Spine and Trunk Muscles

Terms referring to sides:

• Bilateral
• Unilateral
• Contralateral
• Ipsilateral

Examples of uses of the term "bilateral"

• Joint Actions and Muscles: Most muscles in the human body are paired, occurring on both sides. When they contract unilaterally or bilaterally, muscles may contribute to different joint actions. For example, the internal obliques contribute to spine/trunk flexion when they contract bilaterally but contribute to ipsilateral flexion or ipsilateral rotation when they contract unilaterally.
• Exercise science: Many exercises are performed unilaterally, that is, with one arm or leg. Examples include a unilateral rope row , single-leg touchdown , or unilateral dumbbell chest press .