061019 The Effects of Aging
We tend to think our bodies deteriorate due to the aging process but the truth of the matter is being sedentary most of the time is the major culprit. In addition to being sedentary, there are physiological reasons that our bodies deteriorate, as we grow older.
According to the current research there are at least five neuromuscular changes within our body that have a direct effect on this age-related loss of muscle mass commonly referred to as sarcopenia.
- Shrinking of the muscle fibers occurs within the cross-sectional areas of all muscle fibers. This is especially true in the fast twitch type II fibers. These fast twitch fibers are the power and strength producing portions of the muscles that help prevent falls and assist in the daily tasks of lifting objects and moving about.
- There are fewer motor nerves with a corresponding increase in the size of the remaining motor units. It is known that when a motor nerve, typically fast twitch, dies off because of the aging process all of the muscle fibers these nerve support also die off. A few fibers remain which are innervated by neighboring motor nerves. However, this innervation tends to increase the size of the motor units thereby changing the existing ratio between the slow twitch and fast twitch fibers within the muscle. This change results in more, slow twitch fibers.
- The neuromuscular junction experiences structural changes due to the aging process. From this junction, the nerve sends its chemical signal to activate the muscle. One of the changes that takes place is an unraveling in the folds on the muscle cell membrane. These folds contain receptors that receive the chemical message sent by the nerve controlling the muscle. Subsequent to this unraveling, the cell membranes flatten out. This increases the distance between the receptors, which reduces the quality of the signal.
- An additional structural change involves the myelin sheath. The myelin sheath is a fatty type of insulation that wraps around the nerves thus preventing short-circuiting between nerves in close proximity to one another. There is an encroachment of this myelin sheath between the muscle cell and the nerve signaling port called the synaptic cleft. This intrusion partially blocks the chemical message sent from the nerve to the muscle thereby weakening this transmission. Both of these structural changes, the unraveling and the myelin sheath encroachment, reduce not only the speed of the transmission but the quality of the messages emanating from the nerves to the muscles. The ultimate result of these two changes adversely affects how the muscles contract.
- As a person ages, there is a reduced amount of calcium flowing inside the muscle. Consequently, this leads to a less powerful contraction. It is this less powerful contraction that increases the potential of falling. Why, you may ask, is this the case? Briefly, let me explain. If you recall from your school days when the formula for power was written on the blackboard it showed this formula: power equals mass (work) over time. In this case, if you have a less powerful contraction of your lower torso muscles, it means it is going to take you longer to regain your balance if you begin to fall simply because the capacity of your muscles to exert power has been reduced.
- There are fewer immature cells surrounding the mature muscle fibers. These immature cells not only produce new fibers but they are also able to fuse two existing muscle cells into one that then controls the protein synthesis within this muscle tissue. So the loss of these immature cells decreases the potential of the muscle to both repair and increase the hypertrophy of the muscle.
It is essential to stay active, to engage in physical exercise and maintain a high level of fitness into our old age. This following chart* clearly tells the story of aging with and without exercise.
|Determining Factors||Aging without exercise||Aging with Exercise|
|Percent of Body Fat||Increases||Decreases|
|Percent of Lean Tissue||Decreases||Increases|
|Blood Pressure numbers||Increases||Decreases|
|Range of Motion (also known as flexibility)||Decreases||Increases|
|Bone Mineral density||Decreases||Increases|
*Unknown author or origin
A simple comparison of the lists quickly shows that exercise is vital to living a healthy life. The old adage of use it or lose it certainly applies here.
True fitness is a combination of four, at minimum, physical elements, each supported by the mental component.