It is not normal reaction of doing exercises. Exercises might get your mind focus out, yet as to blurry vision, although it might be some simple and common eye condition, it might indicate certain healthy problem, which needs your immediate attention. Normally it is accompanied with dizziness, nausea, difficulty of concentration and breathing, and especially fatigue and thirst. The most common cause of blurry vision during or after exercises is low blood pressure, hypotension in medical term. I am suffering from hypotension so that I am easily tired, and sometimes I feel giddy and faint. Dehydration, allergy or nutrition deficiency might bring these uncomfortable feelings to you. People with pigmentary glaucoma might experience the blurred vision brought from exercises too. You can sit down to have a rest. Drink a cup of water slowly and take a small snack to relieve the symptom. If you have any allergic reaction, then get fresh air and be away from the allergens.