Normal blood pressure is usually 120/80 mm Hg (systolic/diastolic). In healthy people, especially athletes, low blood pressure is a sign of good cardiovascular health (heart and blood vessels). But a low pressure may signal an underlying problem, which can cause inadequate blood flow to the heart, brain and other vital organs. In any individual, a pressure drop of about 30 mm Hg in relation to their usual pressure, or systolic pressure below 90 mm Hg can be diagnosed as hypotension (Cunha, 2011).
The circulatory system is the anatomical structure that covers both cardiovascular system, and the lymphatic system, which leads the lymph. Blood is a specialized type of connective tissue, with a matrix and a liquid colloidal complex constitution. It has a solid phase (formed elements, including the white blood cells, red blood cells and platelets) and a liquid phase, represented by the blood plasma. Lymph is a clear liquid that runs through the lymphatics and usually lacks pigment. Lymph comes after the excess fluid from the capillaries into the interstitial space or intercellular, being picked up by the lymphatic capillaries that drain lymph vessels thicker ducts converge to empty into the subclavian veins.
Nervous system is a type of organ which consists of a network containing a set of specialized cells called as neurons.
正常的血压通常是120 / 80毫米汞柱（收缩压/舒张压）。健康的人，特别是运动员，低血压是心血管健康良好的标志（心脏和血管）。但是低气压可能预示着一个基本的问题，这会导致血流量不足的心脏，大脑和其他重要器官。任何个人，约30毫米汞柱与通常的压力的压力降，或收缩压低于90毫米汞柱，可诊断为低血压（库尼亚，2011）。