Regularly stretching a muscle increases its flexibility and improves circulation to the area. However, you may have noticed that stretching a muscle beyond its optimal length reduces its ability to contract. This phenomenon, which may be seen in a variety of exercises, including flexibility exercises, occurs because of the structure and function of muscle tissue. An overstretched muscle contracts with less force than a slightly extended one because of the underlying mechanism responsible for muscle contraction.
Skeletal Muscle Structure
Skeletal muscles are bundles of individual muscle fibers that are anchored to bones by the tendons located at the end of each muscle bundle. Both thin and thick muscle fibers are present in these bundles and overlap in areas known as the sarcomere, where muscle contraction occurs. In a relaxed muscle, the muscle overlapping areas are at rest and appear to be flattened.
When a muscle is contracted, the overlapping areas shorten as the thin filaments are propelled inward. As you contract muscle, specifically the muscles in your upper arm, a noticeable bulge forms. The decreased muscle length causes the length of the muscle to decrease, as there is a greater area of overlapping muscle fibers in a contracted muscle. As you release the muscle, the muscle becomes flattened again and you begin to lose force as the distance of overlapping muscle decreases.
Overstretching a Muscle
Since the overlapping areas of muscle are responsible for the contraction force, overstretching a muscle decreases its ability to contract. Overstretching pulls the muscle fibers apart so that they no longer overlap. If these fibers can't make contact, no force can be generated, and muscle contraction won't occur. You may notice how much easier it is to contract a slightly bent muscle than one that is overextended. The increased overlap of muscle fibers results in the greatest force possible.
Importance of Stretching
While overstretching a muscle causes decreased force, stretching should still be included as a part of your exercise routine. Stretching increases flexibility, improving physical performance and reducing the risk of injury. Additionally, stretching a muscle increases blood flow, which prevents early fatigue and muscular stiffness. Taking proper care to avoid overstretching a muscle reduces injury and ensures that muscular force is not decreased.
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