Objective
To determine the effect of cold air therapy on relieving spasticity, the optimal intramuscular temperature, and the duration of spasticity relief.

Method
Twenty-three 4 months old Korean white rabbits weighing 2 to 3 kg were used. After posterior laminectomy at thoracolumbar junction, the spinal cord was completely transected. After spasticity occurred, cold air was applied to the triceps surae muscles for 30 minutes at three different intramuscular temperatures (32.5, 30, and 25^oC). Spasticity was measured pre-treatment, immediately following treatment, after 30 minutes, and after 60 minutes. Clinical parameters (muscle tone, deep tendon reflex, ankle clonus, and Babinski's sign) and electrophysiologic parameters (F/M ratio and H/M ratio) were measured.

Result: Muscle tone and Babinski's sign significantly decreased immediately following treatment in the 32.5^oC group, immediately following treatment and after 30 minutes in the 30^oC and 25^oC group. Deep tendon reflex and ankle clonus significantly decreased immediately following treatment in the 32.5^oC group, immdiately following treatment, after 30 minutes in the 30^oC group, immediately following treatment, after 30 minutes and after 60 minutes in the 25^oC group. The F/M ratio and H/M ratio were not significantly affected in the 32.5^oC group but decrease immediately following treatment in the 30^oC and 25^oC groups. Compound motor unit action potentials were not evoked in 6 out of 16 cases (37.5%) in the 25^oC group, resulting in blockage of conduction.

Conclusion
To relieve spasticity with cold air therapy, the intramuscular temperature should be maintained at 30^oC. The duration of spasticity relief lasted from 30 minutes to one hour after cold air therapy.