Muscle-tendon unit

In addition to minimizing the acute inflammatory response, rest prevents additional injury to the affected area.13 The properties of the muscle-tendon unit are altered during the acute injury, with limitations on the ability of the muscles and tendons to stretch. Early activity predisposes a patient to further injury, but prolonged inactivity can lengthen recovery times. 

Intensity of exertion was the most important task variable in two of the three studies explicitly mentioned. The majority (or all) of the morbidity was related to disorders of the muscle-tendon unit. The third study, which considered only CTS, found that repetition was more important than forcefulness (Silverstein et al. 1987). 

Bed et al. (2013) [45] IV 15 (18 knees) 12 US ST 50 % (9/18) Proximal retraction of the amputated stump was observed. Neither normal excursion nor physiological function similar to the native muscle-tendon unit was reproduced... 

Bressel E, M. P. (n.d.). Biomechanical behavior of the plantar flexor muscle-tendon unit after an achilles tendon rupture. Am J Sports Med, 29(3) 321-326. 

Neuromuscular functional units Systems (that is, the combination of nerves, muscles, tendons, ligaments, and so on) responsible for producing basic movements. 

The force generated by muscle contraction is transmitted to bone by tendons, with the muscle-tendon-bone combination forming a functional unit which can be referred to as the musculoskeletal chain. There are important differences between the child, the young adult and the mature adult which account for the different injury patterns that are encountered (Harris 1981). In children, the weak links in the musculoskeletal chain are at the bone-tendon interface and at the growth plate, which accounts for the high occurrence of apophyseal avulsion injuries... 

Even though most natural biological polymers are microscopic, with dimensions on the order of nanometers, they often assemble into a maCTOscopic structure that can be seen with the naked eye. The connective tissue of muscle, tendons, cartilage, and skin can appear stringy when stretched and teased apart. Even bone, lung, nerve, and other tissue have apparent millimeter-scale structures which belie the fact that their true functional units are really much smaller. 

The authors of this chapter have studied the effect of C and D toxin serotypes, as well as A, B, and E, on human intercostal muscle (Hihnas, unpublished data). All serotypes showed a similar ability to produce complete muscular paralysis in ex vivo human intercostal muscle. Intercostal muscle was excised from patients receiving a thoracotomy and intercostal muscle flap procedure. The muscle was removed tendon to tendon by surgical excision without electrocautery and dissected into multiple bundles with their associated intercostal nerves. The nerve-muscle units were placed in a vertical twitch bath and stimulated at 0.03 Hz (0.2 ms pulses of supramaximal strength) using a novel nerve clamp electrode to illicit an indirect muscle twitch. Potent toxins (1 nM) from various serotypes were added to the bath after confirming the stability of control muscle responses. In each case, twitch tensions declined to negligible amplitudes by 1 h after direct toxin application to the tissue bath. 

A few studies have examined the effect of hypothyroidism on the conduction velocity of action potential propagation in mixed nerves. In both hypothyroid rats and humans, nerve conduction velocity was either unchanged (Quattrini et al., 1993) or modestly reduced (Dyck and Lambert, 1970 Rao et al., 1980). Since these studies examined mixed nerves, a selective effect on motor axons can be obscured. Indeed, as mentioned above, we found that hypothyroidism reduced axon diameters only in type S motor units in the rat diaphragm muscle (Prakash et al., 1996a). GhnicaUy, hypothyroidism results in prolongation of the deep tendon teflex (Swanson et al., 1981), likely related to the slowing of conduction velocities in sensory and/or motor axons. 

Muscle contraction dynamics include the mechanical properties of muscle tissues and tendons, which are expressed as force-length and force-velocity relations. The activation dynamics include the voluntary and nonvoluntary (reflex) excitation signal and motor unit recruitment level in the muscle. It is well known that regardless of fatigue, the generated torque in each joint is dependent on muscle activation levels (MALs) and joint angle when in a stationary position. This was first observed by Tnman et al. 

---