Final answer:
In the inverse muscle stretch reflex, certain Ib afferent fibers inhibit antagonist muscles, causing muscle relaxation.
Step-by-step explanation:
In the inverse muscle stretch reflex, certain Ib afferent fibers inhibit antagonist muscles, causing muscle relaxation. This statement is true. When a muscle is stretched, muscle spindles are activated, which send sensory information to the spinal cord. In response, Ib afferent fibers release inhibitory signals that prevent the motor neurons of antagonist muscles from firing, allowing the agonist muscles to relax.