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Body Systems: The Basics
Published in Karen L. LaBat, Karen S. Ryan, Human Body, 2019
Some muscle features are relatively consistent from one muscle to the next. Muscles generally have a red or pink, “meaty” muscle belly, which is relatively thicker and at the muscle center. Muscle fibers form the belly. A tough thick band—a tendon; or a flat sheet—an aponeurosis, anchors the muscle (most often to bones) on either end. These two anchoring structures are formed from opaque, non-contractile connective tissue. They are the accumulation of all the fine connective tissue strands and coverings described in the five levels of muscle structure. While tendons are sturdy connections that facilitate motion, they are vulnerable to damage. Tendonitis is an inflammation (a combination of pain, swelling, and warmth in the tissues) or irritation of a tendon caused by repetitive motions or damage from minor impacts. If an athlete ruptures his/her Achilles tendon, which attaches the calf muscle to the heel bone (calcaneus), the result is pain and immediate loss of strength. Wearable products have been developed as aids in rehabilitation (the restoration of satisfactory function) for both tendonitis and tendon ruptures.
Anatomy, Biomechanics, Work Physiology, and Anthropometry
Published in Stephan Konz, Steven Johnson, Work Design, 2018
Tendons, which transmit force from muscles to bones, have a very high modulus of elasticity (close to mild steel!) and very high tensile strength (45 to 125 N/m2). See Figure 2.19. Synovial sheaths, containing a lubricant called synovial fluid, often (but not always) surround the tough, ropelike tendon. A tendon in a sheath is like a wire in a soda straw. A strain is the tearing apart of tendon fibers (akin to fraying a rope). Tendinitis (also called tendonitis) is the inflammation of the tendon. Tenosynovitis (also called tendosynovitis, tendovaginitis, and peritendinitis) results when the sheath produces excessive synovial fluid, making the sheath swollen and painful. Tendons have virtually no blood supply, and thus, they heal very slowly. An inflammatory reaction may begin in the damaged tendon area. The inflamed tissue carries with it a blood supply for tendon repair, but it also has a nerve supply that can cause severe pain.
Tenosynovitis
Published in Richard Graveling, Ergonomics and Musculoskeletal Disorders (MSDs) in the Workplace, 2018
Chipman et al. (1991) also used the term tendonitis to cover the various disorders listed earlier, including specific tenosynovitis. The authors stated: Tendinitis occurs in people who subject their musculotendinous structures to an acute unaccustomed use or a chronic repetitive motion that exceeds the tolerance of the tendons or their sheaths. Examples include (1) well-trained athletes who abruptly increase their workout intensity, (2) manual task employees who change jobs or increase their work speed.
The effects of pistol grip power tools on median nerve pressure and tendon strains
Published in International Journal of Occupational Safety and Ergonomics, 2022
Ryan Bakker, Mayank Kalra, Sebastian S. Tomescu, Robert Bahensky, Naveen Chandrashekar
CTS is caused by excessive pressure on the median nerve [10], which runs through the carpal tunnel. During pistol grip power tool operation, changes to the median nerve pressure (MNP) can be caused by gripping the handle [2,11–13] and deviating from a neutral wrist position [13–15]. Tendonitis is inflammation of a tendon caused by cumulative trauma through repetitive strain [16]. The tendons of the flexor digitorum profundus (FDP) and flexor digitorum superficialis (FDS) muscle groups travel through the carpal tunnel and are responsible for applying grip force and engaging the tool trigger during power tool operation. These tendons are commonly associated with tendonitis [17,18]. While muscular contractions cause these tendons to experience strain during hand-tool gripping tasks, the tendons may experience additional strain from a forceful tool handle rotary displacement due to a reaction torque at the end of a fastener’s travel.