-DG
Base element impairments: When impairments are present, one cause of the impairment may be the presence of an atrophied muscle. In this case, the muscle isn’t properly functioning due to decreased cross-sectional area and loss of parallel contractile components. Decreases levels of connective tissue as well as loss of sarcomeres in series are also concomitant issues seen with atrophy. When muscles are atrophied, the necessary strength required for joint stabilization or joint centration are limited and therefore compensatory actions occur that place the joint in a compromised position. When a muscle is atrophied, it is unable to hold the limb in the manual test position or at any point in the range when resistance is applied. The muscle is not painful when palpated or when contracting against resistance. To return the weak muscles to normal strength, careful attention must be paid to assess whether it is a local or general atrophy. When local atrophy is the culprit, strengthening in an isolated, low load position is recommended to ensure the muscle itself is strengthened without adding to the dysfunction and perpetuating the problem.
Muscle length changes that occur with prolonged postural habits are often causes of movement impairment syndromes. In such cases, chronically short, versus chronically long muscles require proper attention to the length-tension relationship and may need to be strengthened in their respective position of optimal motion, rather than either applying strengthening through the entirety of the ROM. When a muscle is chronically short, the relationship of the length-tension curve compared to that of a normally functioning muscle is a decrease in absolute force generated, but with an observable greater tension in the shorter joint ranges of motion. The opposite happens to be true with a chronically lengthened muscle; the muscle produces greater absolute force at peak force, but the relative force produced at any given lower range of motion will be less than that of the normal length muscle. In the case of the chronically short muscle, a stimulus to add sarcomeres in series must be accomplished in order to achieve the desired range of motion, and to return the normal function. It is recommended that a stretch stimulus of low level is achieved for about 20-30 minutes two to three times per day. In the case of the chronically lengthened muscle, exercise must be done in the ROM in which the length-tension ratio is not optimal, usually in a gravity reduced state or possible with assistance until the strength of the muscle in that ROM is achieved. The overall goal of either intervention is that of shifting the length-tension curve with either the addition, or subtraction of sarcomeres in series.
Compensatory relative flexibility is characterized by inadequate joint relationships of muscles in which compensatory actions are observed. In such cases, the joint motion compensation observed isn’t necessarily due to short or stiff muscles, but rather due to the relative stiffness of the muscle to the surrounding antagonists, synergists and stabilizers. When the relative stiffness of a muscle generating movement is greater than that of the stabilizer, or antagonist, then the compensation at the joint is due to insufficient muscle stiffness in the appropriate muscles relative to the mover. In such cases, it is not flexibility, or length that is required, but stiffness in the supporting structures of the muscles that control the joint in question when the compensation is observed. In these cases, the goal of the trainer is then to increase the stiffness of those muscles that require increased stiffness, decreased stiffness (and in some cases increased flexibility) of those muscles which are relatively stiff and short. It is important in these cases where the relative stiffness of the muscles around such joints with compensatory motions is assessed. Only stretching a muscle in which the antagonist is of relatively less stiffness is not going to change the compensation at the joint, one must also increase the stiffness of the antagonist to achieve the desired joint range of motion without the compensation.
