title: Exercise Physiology: Human Bioenergetics and Its Applications
author: George A Brooks Dr.
description: Dr. George Brooks is Professor VII; Director, Exercise Physiology Laboratory at The University of California - Berkeley.
zlib_text: 408 ✦ CHAPTER TWENTY
  ◗ Metabolism
  Nutrients absorbed from the digestive tract are used for
  all the cellular activities of the body, which together
  make up metabolism. These activities fall into two cat-
  egories:
  ◗ Catabolism, which is the breakdown of complex com-
  pounds into simpler compounds. Catabolism includes
  the digestion of food into small molecules and the re-
  lease of energy from these molecules within the cell.
  ◗ Anabolism, which is the building of simple compounds
  into substances needed for cellular activities and for the
  growth and repair of tissues.
  Through the steps of catabolism and anabolism, there
  is a constant turnover of body materials as energy is con-
  sumed, cells function and grow, and waste products are
  generated.
  fatigue, so the body is forced to rest and recover. During
  the recovery phase immediately after exercise, breathing
  restores the oxygen needed to convert lactic acid back to
  pyruvic acid, which is then metabolized further. During
  this recovery phase, re