The influence of muscle relaxers on physiologic processes and exercise

 Diazepam is just one of many muscle relaxers. Diazepam works by inhibiting the excitability of the central nervous system, or CNS. This happens when Diazepam binds to receptors at GABA synapses and boost the GABA inhibiting effects. This mechanism allows Diazepam to act as a muscle relaxer, and increases the GABA effect on alpha motor neuron activity in the spinal cord. One side effect of this drug is relaxation of the skeletal muscle, which will lead to sedation and less general motor activity. This can help someone who is recovering from a musculoskeletal injury. The sedation leads the patient to rest, which will lead to better healing during the initial time after the injury. Another side effect of this drug is not good. If a patient continues to use this drug, they can become addicted. Withdrawal symptoms can include seizures, anxiety, agitation, tachycardia, and sometimes death. This drug is best used for short-term relief for an injury.

Physiotherapists often use Diazepam and Baclofen to help patients. In patients without complications like stroke or a traumatic brain injury, these drugs can interfere with normal neuron changes that help improve motor activities. Lundbye-Jensen, J., Neilsen, J. B., Peterson, T. H., & Willerslev-Olsen, M. (2011) studied healthy patients learning a visuomotor skill. They taught the skill to 16 healthy subjects and used the primary motor cortex leg area in the brain to create responses in the anterior tibialis muscle. The authors found that Diazepam and Baclofen interrupt some of the neuroplastic changes that help patients improve their motor performance. Physiotherapists should use these medications with much caution, especially in healthy subjects. 

Botulism Toxin, after being purified from botulism, also works as a muscle relaxer. It attaches to presynaptic terminal membranes in the skeletomuscular junction. After binding, it destroys proteins that help to make acetylcholine. When it is injected into a specific muscle, the muscle is less exciteable, due to the smaller amount of acetylcholine. This allows the muscle to relax. It can also be used to help someone dress better, wash their hands, and other activites of daily living that use extension in the wrist, elbows, and fingers.

Like many other muscle relaxers, using botulinum can have adverse effects. Long term use inhibits the release of acetylcholine. A decrease in acetylcholine levels causes the muscle to relax, but a lack of acetylcholine paralyzes the muscle fibers. The paralysis in those muscle fibers can spread, and cause loss of function in the muscle.