Muscle Spasms / Wasting is a sudden and involuntary contraction of one or more of your muscles. If you’ve ever been awakened in the night or stopped in your tracks by a sudden charley horse, you know that muscle cramps can cause severe pain. Though generally harmless, muscle cramps can make it temporarily impossible to use the affected muscle.

Causes of Muscle Spasms / Wasting

• Inadequate blood supply. Narrowing of the arteries that deliver blood to your legs (arteriosclerosis of the extremities) can produce cramp-like pain in your legs and feet while you’re exercising. These cramps usually go away soon after you stop exercising.
• Nerve compression. Compression of nerves in your spine (lumbar stenosis) also can produce cramp-like pain in your legs. The pain usually worsens the longer you walk. Walking in a slightly flexed position — such as you would use when pushing a shopping cart ahead of you — may improve or delay the onset of your symptoms.
• Mineral depletion. Too little potassium, calcium or magnesium in your diet can contribute to leg cramps. Diuretics — medications often prescribed for high blood pressure — also can deplete these minerals.
• The muscles are trying to protect themselves from muscle strain 
  A back spasm can occur after any type of strain or injury to the soft tissues—the muscles, tendons or ligaments—in the spine. Following the general treatment guidelines below and the recommendations from your doctor or physical therapist will go a long way in relieving your pain, and your back muscles should calm down in a week or so.
• The muscles can spasm in response to an underlying anatomical problem
  If your back spasm does not get better in 1 to 2 weeks, or it comes and goes over time in the same area of your back, you may have an underlying anatomical problem in your spine.

Details coming soon

Reference