Jogging has a range of physical and mental benefits -- your waistline, heart and lungs, leg muscles and sense of tranquility will all be positively impacted. Jogging stresses almost every physiological system and produces visible changes throughout the body. You may notice that your own skin or that of a training partner becomes white or pale while you're running, either generally or in a localized manner. This is usually benign, but may be cause for concern.
Blood Shunting
The most frequent cause of white skin while jogging is a shunting, or redirection, of a high proportion of your blood supply to your working muscles. Blood that normally courses through the small vessels close to the surface of your skin instead flows through the leg muscles to meet their increased oxygen demands. This effect is more pronounced in cold weather, when less blood needs to remain close to the surface of your skin to dissipate heat, and when you are running very hard.
Anemia
Many joggers suffer from iron-deficiency anemia, a condition marked by low levels of hemoglobin, the portion of red blood cells, or RBCs, that binds to oxygen -- so that the RBCs transport oxygen to the muscles and tissues. Prominent symptoms include white skin, fatigue and malaise. Joggers are more susceptible to anemia than sedentary people. The main reason for this is the mechanical destruction of RBCs as a result of repetitive impact forces -- some 1,500 footstrikes per mile. In addition, joggers often restrict meat intake and hence iron ingestion, and in warm conditions they also lose significant amounts iron while sweating. In most cases, iron supplementation, guided by your doctor, is necessary to restore iron levels to their normal values.
Frostbite
According to the website Running Planet, frostbite has four stages. The first, early-cold response, is characterized by cold, painful feeling and a red skin color. In the next stage, frostnip, your skin may become numb and it takes on a white color -- once this occurs, you need to get inside quickly to forestall permanent damage. If frostnip progresses to superficial or deep frostbite, in which your skin becomes firm, you need to seek immediate medical attention.
Vitamin B12 Deficiency
Insufficient intake of substances besides iron can lead to RBC derangements. A deficiency in vitamin B12, or cyanocobalamin, is known as pernicious anemia. Accordingly, it causes many of the same symptoms of iron-deficiency anemia, including dizziness, fatigue, shortness of breath and white skin. Left untreated, pernicious anemia can also cause neurological symptoms, such as tingling in the hands and feet, forgetfulness and mental status changes. Treatment of mild cases includes dietary modification and oral B12 supplements, while more severe instances require injections of the vitamin, sometimes for life.
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