Lower limb immobilization is associated with increased corticospinal excitability

Temporary immobilization of the leg serves as a useful model for the brain's adaptive responses to casting, long-term confinement to bed rest and possibly to trauma. As part of a larger program using TMS to investigate changes associated with bed rest, we sought to determine whether casting of the leg causes brain excitability changes measurable with TMS, and the time course of resolution of these changes. In this study, eight adults wore a full leg cast for 10 days. TMS measures of motor cortex excitability were gathered before the cast was placed, and then immediately after cast removal, and 24 and 48 h later. A control group did not wear a cast and underwent the same TMS sessions. Significant excitability changes occurred and peaked at 24 h post cast removal in the TMS experimental group but not the non-casted group.