Diseases and Disorders of the Muscular System

Muscular System Diseases and Disorders: A Comprehensive Study Guide

The muscular system is responsible for movement, posture, and vital bodily functions such as circulation and digestion. With over 600 muscles in the human body, it's not surprising that this complex system is susceptible to a variety of diseases and disorders—many of which can be painful, limiting, and difficult to manage.

Below is an educational overview of common muscular system conditions, along with additional information to support your studies and revision.

1. Fibromyalgia (formerly known as fibrositis)

A chronic condition characterized by:

• Widespread pain, tenderness, and stiffness in muscles, joints, and tendons
• Fatigue, even after adequate sleep
• Restless or unrefreshing sleep
• Cognitive issues (often referred to as "fibro fog")
• Anxiety, depression, and irritable bowel symptoms

Did you know?

Fibromyalgia affects around 2–4% of the global population, with women being diagnosed seven times more frequently than men.

It is classified as a central sensitivity syndrome, meaning the brain and spinal cord process pain differently in those affected.

2. Muscle Spasms (Cramps)

Involuntary, often painful, contraction of one or more muscles. Common causes include:

• Vigorous exercise or overuse
• Dehydration or electrolyte imbalances (e.g. low sodium, potassium, magnesium)
• Poor blood circulation
• Sometimes a side effect of medication

Quick fact:
Cramps often occur in the calves or feet, particularly at night, affecting nearly 60% of adults over 50.

3. Muscle Fatigue

Occurs when a muscle cannot maintain its strength of contraction after prolonged activity. Contributing factors:

• Oxygen debt and build-up of lactic acid
• Accumulation of hydrogen ions (H+) lowering muscle pH
• ATP depletion, leading to decreased efficiency

Note:
This is a temporary condition and typically resolves with rest and hydration.

4. Hypotonia

A condition involving decreased muscle tone. Characteristics:

• "Floppy" muscles
• Delayed motor skill development in infants and children
• Poor posture, joint instability

Associated disorders:
Can be a symptom of neurological conditions such as cerebral palsy, muscular dystrophy, or Down syndrome.

5. Muscle Atrophy

Wasting or shrinking of muscle tissue due to:

• Disuse, such as in immobilization or sedentary lifestyle
• Poor nutrition
• Neurological injury (e.g., spinal cord injury, stroke)
• Chronic diseases such as ALS (Amyotrophic Lateral Sclerosis)

Stat:
Muscle mass can decline by 3–8% per decade after age 30, accelerating after 60 (sarcopenia).

6. Myositis

An umbrella term for muscle inflammation. Can be:

• Autoimmune-related (e.g., polymyositis, dermatomyositis)
• Infectious (viral or bacterial triggers)
• Medication-induced (statins are a common cause)
• Symptoms include:
  • Weakness
  • Swelling
  • Muscle tenderness or pain

7. Muscle Strain (Tear)

A tear in muscle fibres or the surrounding fascia, classified into:

• Grade I: Mild overstretching
• Grade II: Partial tear
• Grade III: Full rupture

Common causes:
Sudden movements, overuse, poor warm-up routines.

8. Muscle Spasm vs. Muscle Spasticity

Spasm: Short-lived, involuntary contraction often caused by overuse or injury.

Spasticity: Sustained muscle stiffness due to neurological injury (e.g., from cerebral palsy, stroke, or multiple sclerosis).

Spasticity results from:

Loss of inhibition from the brain or spinal cord

Disrupted balance between excitatory and inhibitory signals

9. Sprain

An injury to ligaments (not muscles) around a joint. However, sprains can affect surrounding muscle function due to:

• Inflammation
• Swelling
• Muscle guarding or spasm
• Often confused with strains, which involve muscles or tendons.

10. Muscle Overuse Injuries

These are common in athletes and can result from:

• Lack of proper warm-up
• Repetitive strain
• Insufficient rest and recovery
• Improper technique

Symptoms include:

• Muscle pain and tenderness
• Reduced flexibility
• Chronic inflammation

11. Muscle Tension Due to Stress

Excessive muscle tension caused by psychological stress is common in:

• Neck
• Shoulders
• Lower back

Leads to:

• Myofascial pain syndrome
• Tension headaches
• Sleep disturbances

Did you know?
Around 30–50% of adults experience chronic muscular tension related to psychological stress.

Final Thoughts

Understanding muscular disorders is vital for anyone studying health, therapy, or anatomy. Many of these conditions can significantly impact quality of life, mobility, and mental health.

If you're training as a massage therapist, physiotherapist, or in any healthcare profession, having in-depth knowledge of these conditions will enhance your ability to:

Recognize signs and symptoms

Refer appropriately

Work safely and effectively with affected individuals

Tip for Revision:
Create flashcards for each disorder, including symptoms, causes, and treatment approaches, and use mind maps to link conditions with affected muscle types, nerves, and body systems.

 

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