Both men and women lose cortical and trabecular bone mass throughout adulthood; men more slowly, and women more rapidly after menopause, which leads to increased risk of fracture. Calcium resorption from bone, rather than diet, increases with aging as parathyroid hormone levels rise. Subtle losses in height begin soon after maturity; significant shortening is obvious by old age. Most loss of height occurs in the trunk and reflects thinning of the intervertebral discs and shortening or even collapse of the vertebral bodies from osteoporosis, leading to kyphosis and an increase in the anteroposterior diameter of the chest. Added flexion at the knees and hips also contributes to shortened stature. These changes cause the limbs of an elderly person to look long in proportion to the trunk.
With aging, there is a 30% to 50% decline in muscle mass in relation to body weight in both men and women, and ligaments lose some of their tensile strength. Range of motion diminishes, in part due to osteoarthritis. Sarcopenia is the loss of lean body mass and strength with aging. The causes of muscle loss are multifactorial, including inflammatory and endocrine changes as well as sedentary lifestyle. There is substantial evidence that strength training in older adults can slow or reverse this process (Fig. 1).
FIGURE 1. Exercise improves strength and bone mass.
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