Mirror Therapy Reduces Pain and Preserves Corticomotor Excitability in Human Experimental Skeletal Muscle Pain

Abstract

Approaches to preserve corticomotor excitability (CE) are attracting interest as a treatment for pain-induced changes in neural plasticity. We determined the effects of mirror therapy (MT) on skeletal muscle pain. Fifteen healthy adults who received hypertonic saline injections (5.8% NaCl, 0.2 mL) into the first dorsal interosseous (FDI) muscle of the right hand to induce experimental skeletal muscle pain were assigned to either the “MT and injection” or “injection only” group. Post-injection, the “MT and injection” group observed their left index finger abducting and adducting for 4 min, creating the illusion that the right index finger was moving. The “injection only” group remained at rest. CE and pain were assessed by measuring motor-evoked potentials (MEPs) of the right FDI triggered by transcranial magnetic stimulation and the numerical rating scale (NRS), respectively. MEP amplitudes were significantly higher in the “MT and injection” group, a trend that persisted post-MT intervention (MT intervention; p p p < 0.05). Our preliminary results suggested that MT decreases CE and pain in skeletal muscles, potentially preventing neural plasticity changes associated with skeletal muscle pain and providing early pain relief.

Keywords

• corticomotor excitability
• experimental muscle pain
• hypertonic saline
• motor-evoked potentials
• mirror therapy
• transcranial magnetic stimulation