[Effects of physical training and age-induced structural and functional changes in cardiovascular system and skeletal...

Age-related morphological changes in the cardiovascular system refer to a thickening of the arterial wall as well as a diffuse increase in the wall thickness of the myocardium. In terms of function, this leads to a decrease of the myocardial contractility in systole and to a delay of the diastolic myocardial relaxation. At the arterial wall, an impairment of wall elasticity as well as a decrease of the vasoreagibility can be observed. The systolic blood pressure and the blood pressure amplitude rise; the blood flow-dependent vasodilatation mediated by endothelial cells decreases. The loss of cardiac pacemaker cells by approximately 90% from the 2nd to the 8th decade leads to a reduction of the heart rate variability and to a decrease of the maximum heart rate during exhaustive physical exercise. Hemodynamically these changes resulted in a continuous decline of the maximum cardiac output as well as the maximum oxygen transport capacity. Between the 3rd and 8th decade the peripheral skeletal muscle mass decreases as a result of a reduction of the size and the number of muscle fibers with an overproportional loss of 30-40% regarding the highly glycolytic type IIb fibers. Furthermore, the intramuscular capillarization declines so that, with a concomitant decrease in the number and size of the mitochondria, the supply with oxygen and energy sources and consecutively the aerobic muscular energy metabolism decreases by 8-10% per decade beginning with the 4th to 5th decade. Additionally, the maximum and explosive muscular strength decreases by 30-35% from the 4th decade onwards. In older, healthy men who perform a regular aerobic muscular training in endurance sport disciplines (e.g., walking, jogging or cycling), a decrease of the resting heart rate, a restoration of the primarily lowered heart rate variability, an improvement of the early diastolic left-ventricular filling as well as a significant increase in the VO2max could be proven. Other studies showed that regular endurance training on a cycle-ergometer resulted in a significant increase in capillarization within the exercising muscle groups. In older, trained individuals a reduced stiffness of the arterial vessel walls and an improved maximum exercise-induced muscular blood supply occurs. In other training studies performed with older subjects, a positive influence of regular endurance training on the carbohydrate metabolism along with an improvement of the primarily reduced insulin sensitivity could be demonstrated. In older men and women who regularly underwent muscular strength training, a significant increase in maximum strength with a significant increase in the proportion of type II muscle fibers was found.