The restorative effect of sleep
It has long been considered that the activity of the muscles and the brain and nervous system throughout the day results in the gradual accumulation, in the body, of chemicals that have something to do with tiredness, or fatigue. We do not know just what these chemicals are, although much research has been done trying to find them in the blood. The removal of these products of fatigue is probably very slow and not complete in the usual recovery period we have discussed. It is thought that only after a good night's sleep is the body really back to normal and ready for another day's exercise and work.
In sleep, the muscles are probably more relaxed than at any other time, except when the body is under the influence of a total anesthetic. The rate of metabolism is reduced up to 20 percent below the basal, or resting, level. When we awake at last, renewed and refreshed, our muscles are ready for the stresses of the-following day.
