Sympathetic nervous activity during exercise.

At onset of dynamic exercise, central command and afferent impulses from working muscles set a basic pattern of sympathoadrenal activity according to the relative work load. In turn this activity is of major significance for cardiovascular, hormonal, and metabolic responses, and, furthermore, influences thermoregulation, water and electrolyte homeostasis, and muscular performance. During continued exercise, impulses from multiple receptors feed back on sympathetic centers, error signals arising from changes in intravascular pressures, plasma glucose concentration, tissue oxygen tension, body temperatures, and possibly in mechanical performance and extracellular potassium concentration. However, far from fully explored is the exercise-induced basic pattern of impulse distribution within the sympathoadrenal system, and this pattern's dependency on type of exercise--e.g. dynamic versus static, and on the state of the organism--e.g. concerning tissue sensitivity to catecholamines or presence of disease. Much research is needed to clarify the interplay between the various central and peripheral afferent inputs both in the control of sympathoadrenal activity in acute exercise and in the adaptation of this activity to various conditions or procedures (e.g. training).