Working out can be physically taxing, depending on your physical condition and the intensity of the workouts you perform. A person who performs strenuous exercises, pushing beyond physical capacity, may experience fatigue from overexertion. However, feeling tired after exercising may also signify an underlying health problem.
Determining Your Fitness Level
Performing workouts that exceed your fitness level will make you feel tired. For this reason, it is always important to consult a doctor before starting an exercise program. During a routine physical exam, a doctor generally checks your blood pressure, cholesterol level and your blood-iron level. If your physician knows that you plan to start exercising, he also may perform a treadmill and electrocardiography tests to determine your active and resting heart rate. The results of your exam will give you knowledge on the types of exercises that you should perform and those that you should stay clear of to avoid overexertion, which can cause you to feel tired.
Hydration
Dehydration is a major cause of fatigue, primarily during and after physical activity. The body needs ample water for organs to work effectively and for joints to move with ease. Without adequate water, the body must work harder to function, which can rob you of energy. Because the body also excretes water throughout the day, it is essential to replace it by staying hydrated through the day, increasing water or sports drink intake during exercise.
Nutrition
A person's nutrient intake affects their recovery from physical activities. Poor dietary choices cause the body to become malnourished, which leads to a decrease in energy. When the body lacks essential vitamins and minerals, it must work harder when performing repetitive movements, such as those required during exercise. Along with drinking ample water, make smart dietary choices. Increase your fruit and vegetable intake, consume adequate protein and eat healthy carbohydrates when fueling your body.
Adequate Sleep
The body needs an adequate amount of rest daily. Without rest, muscles and organs cannot rebuild and regenerate effectively. Continuously using muscles that were not given the opportunity to rejuvenate will tire out your body. Get at least six to eight hours of rest each night for maximum energy.



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