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Longer-term hypertrophy occurs due to more permanent changes in muscle structure. Hirono et al. explained the causes of Muscle swelling: [10] "Muscle swelling occurs as a result of the following: (a) resistance exercise can increase phosphocreatine and hydrogen ion accumulations due to blood lactate and growth hormone production, and
Drive reduction theory, developed by Clark Hull in 1943, is a major theory of motivation in the behaviorist learning theory tradition. [1] "Drive" is defined as motivation that arises due to a psychological or physiological need. [2] It works as an internal stimulus that motivates an individual to sate the drive. [3]
Changes in lean body mass and muscle volume are paralleled by a concomitant decrease in myofiber cross-sectional area (CSA). To date, preflight and postflight muscle biopsy samples have been obtained from only a few crewmembers. In U.S. studies, muscle biopsies were obtained before and after flight from the m. vastus lateralis of 8 astronauts ...
By no means it depends on its mass or length alone. For instance, when muscle mass increases due to physical development during childhood, this may be only due to an increase in length of the muscle fibers, with no change in fiber thickness (PCSA) or fiber type. In this case, an increase in mass does not produce an increase in force.
The muscle fibers belonging to one motor unit can be spread throughout part, or most of the entire muscle, depending on the number of fibers and size of the muscle. [2] [3] When a motor neuron is activated, all of the muscle fibers innervated by the motor neuron are stimulated and contract. The activation of one motor neuron will result in a ...
Conversely, decreased use of a muscle results in incremental loss of mass and strength, known as muscular atrophy. Sedentary people often lose a pound or more of muscle annually. [citation needed] The loss of 10 pounds of muscle per decade is one consequence of a sedentary lifestyle. The adaptive processes of the human body will only respond if ...
Unlike the endomysium, the perimysium has large variations in quantity and organization from one muscle group to another. [12] Muscles contain far more perimysial than endomysial connective tissue, and it has also been observed that the ratio of the dry mass of perimysium to that of endomysium ranges between 2.8-1 and 64–1. [13]
In clinical and experimental studies there is an observed increase in muscle excitability in electrical currents involving chemical actions, while there is a decrease in excitability to current associated with electrical induction in denervated muscles. Changes in the resting membrane potential involving denervated muscles presents mild ...