College of Massage Therapists of British Columbia (CMTBC) Practice Exam

Which characteristic of multiple sclerosis (MS) may affect a patient's ability to contract a muscle during strengthening exercises?

1. Demyelination of motor neurons

2. Loss of muscle mass

3. Impaired blood flow to muscles

4. Decrease in overall muscle strength

The correct answer is: Demyelination of motor neurons

The characteristic of multiple sclerosis that primarily affects a patient's ability to contract a muscle during strengthening exercises is the demyelination of motor neurons. In MS, the immune system attacks the myelin sheath that surrounds and protects nerve fibers. This demyelination disrupts the normal transmission of electrical signals along the nerves responsible for muscle contraction. As a result, the signals sent from the brain to the muscles become impaired, leading to difficulties in initiating and maintaining muscle contractions during exercises. While loss of muscle mass, impaired blood flow to muscles, and decrease in overall muscle strength can also impact a person's strength and functionality, these factors are more indirect effects of the disease or its progression rather than the primary issue at play in muscle contraction. The core problem in MS, particularly concerning muscle contraction during strengthening exercises, is the effect of demyelination on the motor neurons.