What Are the Causes of Feeling Bad After Exercising?

Exercise is known to promote relaxation, battle stress and boost mood. So if you leave the gym feeling sick, it can be a warning sign that you're not doing something properly. Your body may be telling you that you've pushed too hard, or your fluid intake wasn't right. If you don't feel well after exercising, evaluate your pre-workout routine and your workout regimen to figure out why.

A woman is sprinting on a treadmill. (Image: decisiveimages/iStock/Getty Images)


Your body needs plenty of fluids to keep it functioning well -- and if you exercise, it's necessary to increase fluid intake. If you don't drink enough water, your body becomes dehydrated because of the excess fluid loss from sweating during your workout, says the American Council on Exercise. You may feel extremely tired and lethargic, nauseated and experience unusual muscle soreness following a workout if you are dehydrated.


While you need to drink to stay hydrated, it's possible to overdo it with the water. The American Council on Exercise says that most women need around 91 ounces of water daily and men need about 125 ounces. Drinking excessive amounts of water can lead to a condition known as hyponatremia, which occurs when sodium levels in the body are too low. Overhydrating can cause you to feel extremely nauseated following a workout.

Blood Sugar

Your blood sugar levels can change based on the amount and type of food you eat and the intensity of your activities. High blood sugar, from consuming too much sugar in your food without working it off, can cause dizziness and nausea. Low blood sugar, from not eating enough before you exercise and working out too vigorously, can cause the same symptoms. Low blood sugar can also cause shaking and weakness.


You may need to restore your electrolyte balance after a workout. Sweating depletes your body's natural water reserves and will upset the equilibrium. Drink sports beverages to replace the lost electrolytes; and ensure that your diet includes the necessary nutrients that produce electrolytes like potassium, calcium and sodium, among others, to ensure that you feel good after a workout.


Over-training is a common cause of not feeling right after a workout. Over-training occurs when you have pushed yourself too hard and your body responds physically and emotionally from the strain. Over-training can cause moodiness, extreme fatigue and an overall feeling of illness, says the American Council on Exercise. Over-training can also cause persistent pain in the joints or muscles and frequent illnesses due to a weakened immune system.

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