Archivio per il tag 'muscle'

Attività fisica, età e funzioni fisiologiche

Stephen D. R. Harridge and Norman R. Lazarus, Physiology, 32: 152–161, 2017.

At the anatomical level, muscle loss in older people is associated with atrophy of fast-contracting, type II muscle fibers. Indeed, it has been suggested that type II fiber atrophy might completely explain the loss of muscle bulk in later life. However, a prevailing view is that skeletal muscle loss also relates to a loss of muscle fibers secondary to a loss of motor units. Partial re-innervation of abandoned fibers is believed to occur, resulting in an increased size of remaining motor units, with knock-on effects for fine motor control. This hypothesis is supported with histological evidence of fiber-type grouping and through electromyo- graphic estimates of motor unit number.

Whereas evidence of streaming of Z line and rod formation, and angulated fibers further point to dysregulation of skeletal muscle in later life (81). Studies of mas- ter athletes paint a very different picture (as illustrated in FIGURE 3), which once more challenges the assertion that these changes can be explained by an inherent aging process and are inevitable consequences of getting older.

Figure 3. MRIs taken across the mid region of the thigh. Images taken across the mid region of the thigh, showing a sarcopenic muscle (middle) from a sedentary individual with reduced contractile mass, more subcutaneous fat, and infiltration of fat and connective tissue. By contrast, the muscles of a similarly aged master triathlete (bottom) shows little difference to that of a younger athlete (top)