The Centers for Advanced Orthopaedics is redefining the way musculoskeletal care is delivered across the region with locations throughout Maryland, DC, Virginia and Pennsylvania.
Muscle strength is one of several components of an overall fitness program. Skeletal muscles are designed to supply mobility to the body by moving the bones and joints through tendon attachments. Muscles also provide dynamic stability to the joints they cross.
Skeletal muscles are composed of muscle fibers that have contractile abilities and connective tissue that is non-contractile. Muscles are innervated by the nervous system to produce voluntary movement, and develop tension in response to various stimuli.
There are three types of muscle contractions: isometric, concentric, and eccentric. During an isometric contraction the muscle length does not change but the tendon has tension producing a force. The muscle contracts but not enough to create motion at the joint (holding a weight in your hand while keeping your elbow bent at 90 degrees). During a concentric (shortening) contraction there is motion occurring at a joint causing bones to move toward each other. This occurs because the muscle tissue is shortening while the tendon length remains the same (performing a bicep curl). An eccentric (lengthening) contraction allows bones to move away from each other by the muscle tissue lengthening in a controlled manner (slowly lowering the elbow from a fully bent position with a weight in your hand). More tension can be created during an eccentric (or "negative") contraction, followed by isometric and finally concentric.
Various factors affect the overall strength of a muscle including injury, surgery, gender and age. The overall goal of physical therapy is to decrease disability and restore function. Strength training can be one component addressed. During a physical therapy examination, muscle strength is assessed to determine the loss of function and an appropriate treatment program is implemented.
The type of strengthening that occurs during physical therapy is different than the type of strengthening that occurs in a gym setting for bodybuilders. The goal of physical therapy is to restore normal strength. Eccentrics, isomterics and sub-maximal strengthening for endurance are often emphasized in the early stages of therapy. Muscles that are weak can become atrophied due to disuse. Atrophy is the wasting or reduction in size of a muscle due to a decrease in protein synthesis leading to muscle fibers that are not replenished. Exercise during physical therapy helps to restore muscle protein synthesis, which in turn will increase muscle strength and lead to improved function.
By contrast, hypertrophy or "bulking up" of a muscle is an increase in muscle size and volume by the enlargement of the components of a muscle. When bodybuilders use near maximal weights ("as much as they can lift") for strengthening to bulk up, they are starting at normal strength and size of a muscle. As the muscle is stressed there is an increase of protein synthesis and fluid in the muscle tissue. It takes several weeks of continued progressive overload (increased weight, reps, and sets) for hypertrophy to be noticed. Hypertrophy is the goal for body builders, as compared to normalizing strength and function during physical therapy.