ABSTRACT
Muscle cells are characterized by their unique ability to undergo contraction and subsequent relaxation, the former process requiring the expenditure of metabolic energy through hydrolysis of adenosine triphosphate (ATP). There are three types of muscle in humans-cardiac, skeletal, and smooth-but in terms of significance to clinical chemistry, assessments of cardiac muscle function are by far the most relevant. Measurements on skeletal muscle are also useful in certain circumstances but no tests on smooth muscle are made routinely.
