Muscles that span one joint are called unicompartmental muscles, such as the brachialis. Muscles that span two or more joints are called polyarticular muscles, such as the rectus femoris. Due to the number of joints crossed by the multi-joint muscles, there are “active deficiencies” and “passive deficiencies” of the multi-joint muscles at work. 1.Multi-joint muscle “active deficiency” When the multi-joint muscle works as a primary muscle, its muscle force fully acts on one joint and then cannot fully act on other joints, this phenomenon is called multi-joint muscle “active deficiency” (in essence, muscle force deficiency). If you fully flex your fingers and then flex your wrist, you will feel weakness in flexion (the original grip has a sense of release), which is the forearm flexor muscle group occurred in the multi-joint muscle “active deficiency” phenomenon. In sports there is a multi-joint muscle “active deficiency”, should pay attention to the development of the group of muscle strength. 2, multi-joint muscle “passive deficiency” multi-joint muscle as a confrontation muscle appears, has been elongated in a joint, in other joints can no longer be elongated phenomenon, called multi-joint muscle “passive deficiency” (in essence, the muscle extension is not enough). If the knee is extended and then flexed, i.e., the straight leg swings forward, the leg does not swing high, which is due to the occurrence of multi-joint muscle “passive deficiency” in the posterior femoral muscle group. In sports for prone to multi-joint muscle “passive deficiency” muscle, we should pay attention to the development of its stretch, which can play a positive role in improving sports performance and preventing sports injuries. Is it true that active deficits are mainly seen in patients with low muscle strength, while passive deficits are mainly seen in patients with muscle atrophy? If there is an “active deficit” in the multi-joint muscles in sports, attention should be paid to developing the strength of this group of muscles. For muscles prone to “passive deficiency” of the multijoint muscles in sports, attention should be paid to the development of their extension. To put it plainly, one should pay attention to the training of muscle contraction, explosive power, endurance, etc. At the same time, the soft tissues of the antagonist muscles, such as ligaments and tendons, need to be stretched to ensure the magnitude and range of movement, which is also required to improve gait and upper limb movement. In hemiplegic patients, the flexor tone of the upper limb is increased and the five fingers are clenched, so it is difficult to do finger extension and retraction training, but in the case of wrist flexion, the finger tension is significantly reduced and the fingers can be easily extended and retracted. If you fully flex your fingers and then flex your wrist, you will feel weakness in flexing your fingers (a sense of release of the original grip), which is the phenomenon of “active deficiency” of the forearm flexor muscle group. We can use this principle to induce active activity in a dominant position or more fully when treating patients; if the muscle tone is high, you can also help stretch the hand by pressing down on the wrist joint to facilitate further stretching techniques and inhibit spasticity. Is this physiological phenomenon possible in every person? Further explanation: 1. Active muscle deficit When the contraction of the multijoint muscle reaches a certain limit, it can no longer produce effective tension for one of the joints, so it cannot fully function for the other (or the rest of the) joints, a phenomenon called “active deficit” of the multijoint muscle (or active muscle This phenomenon is called “active deficiency” of the multi-joint muscles (or “active deficiency” of the active muscles). Also take the analysis of the action of clenching a fist, when the wrist dorsal extension position or neutral position can be very adequate, but in the case of flexion of the wrist and then flexion of the finger, will feel the lack of power, this is because the flexion of the wrist and then flexion of the finger more than the limits of muscle pull, and therefore limit the action of clenching a fist, that is, the forearm flexor muscle group “active deficiency”. 2, the passive deficiency of muscle When multi-joint muscle is elongated extension, in one of the joints has been elongated, the other (or the rest) of the joint can not be fully elongated, this phenomenon is called multi-joint muscle “passive deficiency” (or antagonistic muscle “passive deficiency “). For example, when the knee is flexed in the supine position, the hip joint can be flexed up to 120°, but when the knee is straightened, the hip flexion is much smaller, which is the phenomenon of “passive deficit” of the posterior femoral muscles. By understanding these characteristics of the multi-joint muscles, the position of each part of the body can be adjusted according to the actual situation in treatment to avoid the “active deficiency” or “passive deficiency” of the multi-joint muscles, so that the strength or extension of the multi-joint muscles can be concentrated on one joint to achieve better To achieve better treatment effect.