section_path: Clinical significance/Atrophy
section_name: Atrophy
paragraph_text: Atrophy
  
  Every day between one and two percent of muscle is broken down and rebuilt. Inactivity, malnutrition, disease, and aging can increase the breakdown leading to muscle atrophy or sarcopenia. Sarcopenia is commonly an age-related process that can cause frailty and its consequences. A decrease in muscle mass may be accompanied by a smaller number and size of the muscle cells as well as lower protein content.
  
  Human spaceflight, involving prolonged periods of immobilization and weightlessness is known to result in muscle weakening and atrophy resulting in a loss of as much as 30% of mass in some muscles. Such consequences are also noted in some mammals following hibernation.
  
  Many diseases and conditions including cancer, AIDS, and heart failure can cause muscle loss known as cachexia.