So many physical abilities decline with normal aging, including strength, swiftness, and stamina. In addition to these muscle-related declines, there are also changes that occur in coordinating the movements of the body. Together, these changes mean that as you age, you may not be able to perform activities such as running to catch a bus, walking around the garden, carrying groceries into the house, keeping your balance on a slippery surface, or playing catch with your grandchildren as well as you used to. But do these activities have to deteriorate? Let’s look at why these declines happen — and what you can do to actually improve your strength and coordination. The loss of muscle mass is related to both a reduced number of muscle fibers and a reduction in fiber size. If the fibers become too small, they die. Fast-twitch muscle fibers shrink and die more rapidly than others, leading to a loss of muscle speed. In addition, the capacity for muscles to undergo repair also diminishes with age. One cause of these changes is decline in muscle-building hormones and growth factors including testosterone, estrogen, dehydroepiandrosterone (better known as DHEA), growth hormone, and insulin-like growth factor.