Make Sleep a Priority Chapter 7

Sleep Helps Your Body Rebuild

Most systems slow down when you sleep, but the body's systems for cell repair and growth kick into high gear.


The Body Shop

Nighttime is when the body's natural repair shop is open for business. A surge of growth hormone is secreted by the pituitary gland during deep sleep, just before the REM phase. All sleepers experience this surge, regardless of their age. But in children and young adolescents, the increase is much larger. Sleep is the time to grow. Growth hormone works with other specific growth factors to build and repair cells. One of these IGF-1 (insulin-like growth factor-1) plays a role in the repair of muscles and bones.

Animal studies have shown that almost no bone growth occurs during waking hours, when the skeleton is supporting movement and the body's weight. Nearly all bone cell creation happens during sleep. Cells called osteoclasts break down old or damaged bone tissue, while other cells called osteoblasts lay down new bone tissue.

Muscle-cell repairs are impractical when a muscle is still doing its work. But during deep sleep, when metabolic processes slow and muscles are motionless, damaged muscle cells are repaired and reinforced. The repair process for muscles involves satellite cells, which are rather like stem cells for muscles. These amazing, multitasking cells can multiply and differentiate to rebuild the muscle cell. They can also join together and fuse to the muscle cell, becoming part of the rebuilt, larger muscle fiber.

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