China
Africa
Explore chapters and articles related to this topic
Body Systems: The Basics
Published in Karen L. LaBat, Karen S. Ryan, Human Body, 2019
Designers and fitness professionals frequently talk about “toned bodies,” in relation to body form. But the definition of muscle tone (also called muscle tonus) relates to a normal responsiveness of muscles to nervous system input, not to size or form. Bernstein gives a concise definition of [muscle] tonus as “not a condition of elasticity, but a condition of readiness” (1967, pp. 111–112). He goes on to point out that tonus is a condition that reflects all the connections from the brain to the muscle, which is related to coordination and readiness “as a state is to an action” (1967, pp. 111–112). A toned body might be considered a trained body but should not be confused with a bulky or an exercised body. See Section 2.6 to consider how adipose tissue, commonly called fat, contributes to body form.
Repetitive TasksRisk Assessment and Task Design
Published in R. S. Bridger, Introduction to Human Factors and Ergonomics, 2017
This primary response may be accompanied by a feeling of soreness in the muscle, which diminishes as the damaged muscle fibers regenerate (Armstrong et al., 1993). In a conscious person, skeletal muscles always have a certain degree of “tightness.” There is a baseline level of muscle fiber recruitment even during relaxation. This is known as muscle tone and it is controlled by the central nervous system and by a feedback system involving the spinal cord and the muscle spindles. Muscle tone is essential for the maintenance of posture. People under mental stress may, without realizing it, develop increased tension in their muscles which they cannot control. At work, the prestressed body part may be a source of pain even though the task loading is mild. A chronic, stereotyped pattern of recruitment of motor units may be the dose which leads to damage of the muscle tissues. Roman-Liu et al. (2013) found increased levels of muscle activity (electromyography [EMG]) of approximately 10%–25% when subjects engaged in sustained attention and vigilance tasks compared to control conditions. Increases in EMG activity were greatest in the shoulder muscles (deltoids and trapezius).
Medical Applications of Ultrasonic Energy
Published in Dale Ensminger, Leonard J. Bond, Ultrasonics, 2011
Dale Ensminger, Leonard J. Bond
Ultrasound causes increased vascular and fluid circulation. Neurogenic effects result in changes in skeletal muscle tone. Associated with ultrasonic irradiation therapy is general relaxation and sedation. Diffusion of chemicals and ions through cell membranes increases, leading to improved organic exchanges as in metabolism and osmosis or to better and more effective utilization of injections. A 3.6-fold increase in the penetration of iodine from a hydrophilic ointment through the skin into the bodies of dogs, rabbits, and humans using therapeutic doses of ultrasound at 800 kHz for 10 minutes has been reported [39]. The early observations resulted in the investigation of ultrasound in transdermal drug delivery [40], in the controlled release of drugs deep inside the body and potentially gene therapy [41], and in the strategies that increase permeability for compound transport through the blood–brain barrier (BBB) [42]. Ultrasound applied to a dialyzer designed for extracting specific fractions of urine increased the extraction rates by several orders of magnitude [43]. Killing efficiency of chemical agents in an ultrasonic sterilizer increased owing to increased transfer rates under the influence of ultrasound.
New scale for assessing spasticity based on the pendulum test
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2022
Antonina Aleksić, Dejan B. Popović
Spasticity often follows a central nervous system lesion (spinal cord injury, multiple sclerosis, cerebral palsy, etc.). Spasticity comes from the imbalance of the neural communication between the central and peripheral nervous systems and results in involuntary muscle activation. This creates an inability to stretch muscles or coordinate movements effectively. Lance (1980) defined spasticity as a motor disorder characterized by a velocity-dependent increase in the tonic stretch reflexes (muscle tone) with exaggerated tendon jerks, resulting from hyperexcitability of the stretch reflexes as one component of the upper motor neuron (UMN) syndrome. Landau (1980) introduced the following definition of spasticity: (1) decreased dexterity, (2) loss of strength, (3) increased tendon jerks, (4) increased resistance to slower passive muscle stretch, and (5) hyperactive flexion reflexes (flexor spasms). Spasticity often results in pain and loss of mobility due to a muscle spasm (Mukherjee and Chakravarty 2010).
RESNA position on the application of dynamic seating
Published in Assistive Technology, 2021
Michelle L. Lange, Barbara Crane, Frederick J. Diamond, Suzanne Eason, Jessica Presperin Pedersen, Greg Peek
Many clients using wheelchair seating have increased muscle tone. This can lead to active extension, particularly at the hips, knees, and neck. When a client extends against a static seating system, the forces exerted against the foot supports, seat, back support, and head support are not absorbed or dissipated, and this can lead to an actual increase in episodes of client extension. It is well known that spasticity increases with resistance, such as client forces exerted against a non-yielding surface (Bar-On et al., 2018). These forces are common in clients with central nervous system diagnoses such as cerebral palsy, traumatic brain injury and Huntington’s disease. Increased muscle tone or spasticity is caused by an imbalance of nerve signals between the central nervous system and the muscles (Bar-On et al., 2015). In addition to increased muscle tone, primitive reflexes and involuntary movements may also be present (Bar-On et al., 2015). Muscle tone is not a constant state. Many clients may appear to be quite relaxed while sitting in their wheelchair seating system. However, many factors can lead to sudden and forceful extension, particularly at the hips, knees, and neck. This extension is often maintained for a short period of time and then subsides. One study found that clients with increased extension were able to exert up to 200% of their body weight against the back support and up to 600% of their body weight against the foot supports during extension (Samaneein et al., 2013).
Thermal and mycological nondestructive active protection of baroque buildings
Published in Science and Technology for the Built Environment, 2019
The impact of IR radiation on the human body is quite well recognized and documented in the extensive literature (Court 2012; Ghahramani et al. 2016). In recent years, especially the medical use of infrared radiation has been broadly examined (Tsai and Hamblin 2017; Rojas and Gonzalez-Lima 2011). Among the benefits of IR radiation impact on human body can be listed the following: Increased blood flow through the dilated blood vessels of the skin.Reduction of muscle tone.Increasing the pain threshold for nerve pain and frostbite.Acceleration of the absorption of exudate in the case of inflammation of tissues.