All people have limitations in their potential performance. In early life, for most people other than athletes, our potential is well beyond the demands that we place on ourselves, so we are not confronted by these limitations. With aging, we experience changes in our physical limitations. Over time, our declining potential performance begins to reach the levels of our daily expectations. Biologically, these changes are related to changes in the cells that make up our bodies. Functionally, the result is that our ability to do things is less than it was when we were younger.
Visual Changes
Normal aging produces changes in our sight that falls under the name of Presbyopia. After age 45 or so, the increasing stiffness of the lens of the eye makes it difficult to focus on objects that are close to us, and many adults discover that they must use reading glasses, or bifocals. In addition, changes to the color of the lens and to the retina at the back of the eye result in a decreased sensitivity to light, so that greater levels of illumination are required for detailed vision. As a result, greater light levels are needed for the same work that we did in our youth, if it is possible at all.
Physical Changes
As we age, the tissues that make up our body become stiffer. (This is one of the reasons for the visual changes noted earlier.) This results in restrictions in movement of our joints, restrictions in the movement of our muscles, and decreased flexibility in our blood vessels. Because few of us are operating at our maximum potential, we may not notice these changes for many years. In fact, a person who is functioning at normal levels into their 50s, and then begins exercising and dieting can experience significant increases in strength and mobility at a time when their maximum potential is decreasing. The maximum potential, however, does not appear to change with diet and exercise. The elder athlete simply uses more of their potential than in the past.
The tissues that make up our joints wear over time. After a long and busy life, we may begin to wear out the linings of the joints and the ligaments that hold them in alignment. This is the condition known as osteoarthritis. Osteoarthritis is not caused by disease, but simply by wear and tear. But, as a result, our fingers may begin to stiffen, and to bend into new shapes. It becomes harder to straighten our arms and legs fully, and we may experience aches and pains after a busy day that we did not feel in the past.
Control Changes
Along with the changes in our eyes, muscles, and joints, we are also experiencing changes in our brains and nerves. Over time, the speed at which a nerve can carry a signal from one part of the brain to another, or from the brain to our foot, for example, decreases. We may experience this as a slowing of reaction time, a decrease in dexterity, or as slight shaking in our hands.
We may also find that we are less able to feel small objects than we were when young. Fine textures may escape us. This change may be a combination of stiffening of the sensory endings in our fingers and the slowing of our nerves.
Physical Changes and the Computer Interface
Over time, the computer has become able to show more and more information, in smaller and smaller sizes. Also over time, the ability of a person to see and process large quantities of fine detail decreases. As a result, today's elders may find the conventional computer very difficult to use. The goal of the Elder Interface Project is to identify the parts of the computer interface that cause difficulty for elders, and to identify free or low-cost changes that will make the interface more usable.