Abstract des Autors

Very little in the scientific literature discusses the effects of overtraining or overreaching on the cardiovascular system. Much has been written regarding cardiac adaptations to chronic exercise training and in general the resultant changes are assumed to be beneficial rather than harmful. These changes include modest increases in chamber thickness and cavity size (physiologic hypertrophy), preserved systolic function, and enhanced diastolic filling. Investigations of the acute effects of a single bout of prolonged exercise are fewer, although several studies have documented transient reductions in cardiac function following very prolonged aerobic exercise, sometimes termed cardiac fatigue. While this may in itself constitute overreaching as far as the cardiovascular system is concerned, no studies have definitively documented the mechanism(s) associated with this decrement in function, although some have been postulated, in part because it is difficult to reproduce cardiac fatigue in the absence of musculoskeletal fatigue and marked changes in fluid and electrolytes and thermoregulation. Indeed, the complex and multiple physiologic changes associated with prolonged exercise are important considerations in documenting the existence and extent of cardiac fatigue itself. Thus, while transient cardiac dysfunction may provide evidence for overreaching, it is difficult to assess the contribution of cardiac dysfunction, if any, to generalized fatigue or decreased exercise performance. Similarly, no studies have documented a progression from overreaching to overtraining as manifest by further cardiac dysfunction. Verf.-Referat