I m 60 years old male with history of hypertension . I jog every week for 40 to 50 minutes. Since last year I experienced loss of vision, dizziness , nausea , excessive sweating when I was jogging and sometimes I just cannot maintain my posture so I have to lie on the floor. But I still remain conscious, my speech and hearing are still normal. After the first time this problem occurred, I take a cup of glucose 30 minutes before jogging. But I still experienced this for quite a number of time. My wife said that I look pale and my hand and feet are cold when I have this problem.