 Long-term endurance training induces many physiological adaptations both centrally and peripherally mediated.Central cardiovascular adaptations include decreased heart rate, increased stroke volume of the heart, increased blood plasma, without any major changes in red blood cell count, which reduces blood viscosity and increased cardiac output as well as total mitochondrial volume in the muscle fibers used in the training (i.e.the thigh muscles in runners will have more mitochondria than the thigh muscles of swimmers).