Why Can Your Vision Get Blurry After Heavy Exercise?

blurred vision during a soccer match

You are in the gym working out and suddenly you can’t see anything for a few seconds.

Is this pretty common? No, it isn’t, but it can happen to anyone.

Blurry vision or temporary loss of vision is associated with heavy exercise and there may a few reasons why that happens. Let us look at but a few common ones.

4 Causes of Blurry Vision During or After Exercise

Hypotension or Low Blood Pressure

Hypotension is a condition when the blood pressure falls too low. Normal blood pressure measures 120/80 mmHg. Anything less than that is considered to be hypotension. Its symptoms include dizziness and a short pulse of vision loss.

The blood pressure is normally at its lowest point about half an hour or an hour after the exercise. Some may experience a more rapid drop. This is a common occurrence any time you exercise but it will be more common when you do not cool down after working out. 

When you exercise, the muscles and heart are working more than they usually do.  They keep the blood pumping so that your muscles can get the oxygen they need. 

When you abruptly stop the exercise, the muscles and heart will quickly return to their normal pace. However, it takes longer for the blood vessels to catch up. This leads to a slower rate of oxygenated blood flowing to the brain. When the brain doesn’t get enough oxygen, it will make you lightheaded or dizzy. 

Remedy: If you experience these symptoms, sit down and put your head between your knees. This posture will help bring oxygenated blood to your brain.

Hypoglycemia

When your blood glucose level falls below the normal and healthy range, the condition is known as hypoglycemia. It occurs when the body’s blood sugar is used up too quickly, the release of glucose into the blood is too slow or when too much insulin is released into the bloodstream.  

Blood glucose levels are represented as milligrams of glucose per deciliter of blood or mg/dL. The blood glucose should not be less than 70 mg/dL. 

It is a common occurrence in diabetic people but it may occur in non-diabetics if they don’t consume enough food before exercise. In general, hypoglycemia doesn’t occur in healthy individuals before or after exercise. 

The signs and symptoms of hypoglycemia include:

  • dizziness,
  • loss of vision or blurred vision,
  • excessive sweating,
  • imbalance or lack of coordination,
  • and fatigue. 

If you are diabetic, you must test your blood glucose before and after exercise to maintain healthy blood sugar levels. After exercise, hypoglycemia can occur because the reduction in muscle glycogen store causes muscle cells to take in a great deal of blood glucose.

Remedy: If you feel hypoglycemic, consume carbohydrates after exercise or a small snack like a banana before exercising. 

Drink a glass of juice as it contains fructose, which is a natural form of glucose that the body can absorb quickly. Eat a high-carb snack or meal 30 and 60 minutes after exercise.

Dehydration

Dehydration is when you lose more fluid than you take in. In that case, the body does not have enough water and fluids to carry out its normal functions. When you exercise, you will lose body fluids in the form of sweating. In case of intense physical work, the loss would be much greater.  

Symptoms of dehydration include:

  • Fatigue
  • Lightheadedness
  • Extreme thirst
  • Dry mouth

Remedy: Hydration is important. Drink water or sports drinks containing electrolytes and carbohydrates before, during, and after exercise. 

Low Oxygenation of Blood

An extreme effort at exercising can cause temporary vision loss. This happens because you are unable to get enough oxygen to the brain. The body is working at all times to maintain balance. It tries to keep normal blood pressure, sugar levels, etc. When you exercise, you challenge your body as it goes out of balance

By pushing the intensity when you exercise, your blood is pumping so fast that it cannot fully oxygenate. It also pumps through the brain so fast that the brain cannot take the oxygen that it needs. At the same time, you are opening up more blood vessels in the body. These get priority and get more blood, making it more difficult to get the required blood volume up to your head. 

The human brain uses up to 20% of the energy used by the entire human body. The brain demands nutrition to function optimally. It is composed of 60% fat and is designed to be fueled by glucose. In fact, the brain accounts for 25% of the total body glucose utilization.

Remedy: If you feel faint while exercising, sit down a few minutes and take slow, deep breaths. The body will slowly go back to its normal, balanced state and the brain will receive the required oxygen.

Glucose is the best food for the brain. Therefore, you must eat foods that are good sources of glucose. These include whole simple carbohydrates like raw fruits or grains, tubers, and legumes, which are whole complex carbohydrates.

Final Say

eye doctor typical exam illustrated

If the vision loss or blurred vision persists, visit an ophthalmologist immediately to eliminate serious, underlying conditions. 

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Eric J. Poulsen, MD

Written by Eric J. Poulsen, MD

Dr. Eric Poulsen completed his medical degree from the University of California-Davis School of Medicine. He was also awarded for Highest Academic Achievement by the UC Davis School of Medicine. He also recived K. Alexander Dastgheib Award for Surgical Skill & Judgment, Alpha Omega Alpha Honor Medical Society. Dr. Eric specializes in performing delicate eye surgeries such as LASIK and PRK. He uses latest techniques for diagnosing and treating cataracts, glaucoma and diabetic eye problems.

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