Prolonged pressure brings about atrophy in the central nervous system as elsewhere. The pressure of an expanding tumour of the membranes covering the brain results in localized atrophy of the adjacent brain substance on which it impinges. In hydrocephalus more widespread atrophy of brain tissue results from the abnormal amounts of fluid confined within the rigid bony compartment of the skull. Increased pressure within the skull may force a portion of the brain through the foramen magnum, the bony opening at the base of the skull, and, if prolonged, results in a localized atrophy of cerebellar tissue pressed against the bony wall.
Concentric muscle contractions occur when a muscle shortens during contraction, as in the upward motion when performing a biceps curl. An eccentric contraction occurs when a muscle lengthens with contraction, as in the "negative" or lowering motion of a biceps curl. An example of an isometric (muscle contracts while maintaining constant length) contraction would be pushing against an immovable object. An example of an isokinetic (muscle has constant speed of contraction) occurs with specialized equipment like Cybex machines. Plyometric contractions occur when a muscle rapidly lengthens just prior to contraction - like during repetitive box jumping.
Woo and Buckwalter describe the mechanisms, barriers, and molecular processes involved in ligament and tendon injury and repair.
The correlation between ACSA and muscular force and/or joint moments is typically around r=-, meaning muscle size only explains about 50% of the variability in force production. Other architectural factors (such as fascicle length and pennation angle) don’t correlate quite as strongly (r=-), explaining about 10-20% of the variation. However, fascicle length and pennation angle also tend to increase with hypertrophy , so it’s less clear whether they independently influence contractile strength (and if they do, their contribution is pretty weak anyways; in fact, Erskine showed that changes in pennation angle and fascicle length may be weakly negatively correlated with strength gains).