I hear so many people complain about muscle and joint stiffness as they get older, especially in the morning. No one really knows how or why people change as they get older. Some theories claim that aging is caused by accumulated injuries from ultraviolet light, wear and tear on the body, by products of metabolism and so on. Other theories view aging as a predetermined, genetically controlled process.
No theory sufficiently explains all the changes of the aging process. Aging is complex. It varies in how it affects different people and even different organs. Most people who study aging feel that aging is the cumulative effect of the interaction of many lifelong influences. These influences include heredity, environment, culture, diet, exercise and leisure, past illnesses and many other factors.
Adolescent changes are predictable to within a few years. This is not true with aging. Each person ages at a unique rate. Some systems begin aging as early as age 30 while other processes are not common until much later. Although some changes typically occur with aging, they occur at different rates and to different extents. There is no reliable way to predict specifically how you will age.
It is unrealistic to try to address all the different factors in aging in this article. However, we will review the present state of knowledge of how the connective tissue in the muscles and joints age causing your morning stiffness.
There are two types of connective tissues that can significantly affect range of motion: fibrous connective tissue and elastic connective tissue. Fibrous connective tissue forms aponeuroses, fascia, membranes, ligaments and tendons. It consists predominantly of collagenous fibers known as collagen.
Collagen is generally regarded as a primary structural component of living tissue. The two major physical properties of collagen fibers are their great tensile strength and inextensibility. They provide the basis for structures such as ligaments and tendons that are subject to a pulling force.
As collagen ages, specific physical and biochemical changes take place. These changes reflect a loss of the minimal extensibility that existed earlier, and reflects an increased rigidity. For instance, aging increases the diameter of the collagen fibers in various tissues. Also, with the passage of time the fibrils become more crystalline. This increase in crystallinity or orientation strengthens the intermolecular bonds and increases resistance to further deformation. Dehydration also occurs with the aging process. The amount of water associated with connective tissues such as tendons declines with age.
Elastic tissue refers to a connective tissue which has elastic fibers as its principal component. It is a primary structural component of living tissue, and is found in various quantities throughout the body. Elastic tissue plays a major role in determining the possible range of extensibility of muscle cells.
Elastic fibers lose their resiliency and undergo various other alterations, including fragmentation, fraying, calcification and other mineralizations. These alterations and others beyond the scope of this article appear to be responsible for age-related loss of resiliency and increased rigidity.
Resource: Science of Stretching