Physical activity requires effective, purposeful movements of your body. These movements are the result of force generated in the muscles that act on the skeleton, according to the National Strength and Conditioning Association. Your muscles contract, or shorten, and relax throughout the day to accomplish physical tasks from blinking your eyes to lifting weights during an exercise session.
Anatomy of Skeletal Muscle
Each skeletal muscle in your body is an organ comprised of muscle tissue, connective tissue, nerves and blood vessels. Muscles have a striated appearance. The striations are actually long, cylindrical muscle fibers about the diameter of a human hair; one fiber can run the entire length of a muscle. Within each muscle fiber, you have two filaments: actin and myosin. These two filaments slide along each other to relax, stretch and contract the muscle as a whole.
Types of Muscular Contraction
Concentric muscle contraction is used when you lift a weight, such as in a bicep curl. The muscle generates force and raises the weight. Eccentric contraction is a lengthening of the muscle tissue with force. This is the lowering portion of the bicep curl where your muscle returns to normal length but you still feel tension. Isometric contraction is where you are exerting force but the length of the muscle does not change. For example, if you are pushing against a wall, you can feel the exertion in your muscles but they do not shorten or lengthen.
Stretching
Stretching is used to lengthen the muscles for better flexibility and range of motion. Through repetitive activity or exercises, muscles can become shortened. This inhibits your movement and can actually begin to cause pain. Stretching the muscle helps counteract these effects to keep you moving in optimal ways. Stretching also increases blood flow to a muscle, according to MayoClinic.com, which is necessary for muscle tissue to perform.
Types of Stretching
Stretching can be active or passive. Active stretching is where you are performing the movement to stretch your muscle, such as raising your leg up in front of you to stretch your hamstrings. A passive stretch is where you are relaxed and something or someone else is stretching your muscles such as in a partner-assisted hamstring stretch. Stretching can also be described as static or ballistic. Static stretching is where you hold the muscle in a lengthened position for a prolonged period of time. Ballistic stretching is where you lengthen a muscle and then bounce to try to lengthen it further. In general, static stretching is more safe than ballistic because you are less likely to pull or injure your muscles.
References
- "Essentials of Strength Training and Conditioning"; National Strength and Conditioning Association; 2008
- University of Nebraska Medical Center: Muscle Contraction
- MayoClinic.com: Stretching
