What Are the Causes of Nausea and Weakness After Exercise

Symptoms of nausea after exercising can stem from a variety of causes. Nausea can be influenced by diet, dehydration or overhydration, and exercising beyond endurance capacity. If each of these potential causes is addressed and nausea persists, seek medical advice. Conditions such as diabetes or heart disease can increase the chances of these symptoms after exercise.

Exercising with undigested food in the gastrointestinal tract can cause digestive distress. Likewise, exercising on an empty stomach also may lead to feelings of nausea. An April 2001 study published in "Appetite" examined the effects of high and low-intensity exercise on subjects who underwent various eating patterns. Each participant exercised on an empty stomach immediately after eating a beef patty and 60 minutes after eating. For comparison, the digestive system also was studied after eating without exercise. Results found that scores for nausea were highest while exercising on an empty stomach and immediately after eating. Nausea was higher if participating in high-intensity exercise directly after a meal. Researchers concluded that exercise can cause nausea, the severity of which is determined by eating patterns.

Lack of and too much hydration may increase the chances of feeling nauseous during or after exercise. The body produces sweat during exercise to help cool its core temperature. Electrolytes such as sodium and potassium are excreted, along with fluids. Depleted levels of fluids and electrolytes during exercise can lead to nausea. The "European Journal of Applied Physiology" published a study in December 2000 that found dehydration delayed stomach and intestine emptying. Delayed gastric emptying induced symptoms of nausea. Overhydration also can cause stomach sickness. Drinking too much water fills the stomach, leading to a bloated feeling.

Hypoglycemia, or low blood sugar, can lead to symptoms of nausea, dizziness, headache and loss of function. Sugar is used by the body to power muscles during exercise. Exercising intensely or for prolonged periods of time can use up the body's glucose reserves, leading to hypoglycemia. Shaking, blurred vision, fatigue and unclear thinking during activity may indicate this condition. Consuming simple carbohydrates and protein can quickly regulate blood sugar, often alleviating symptoms. For those with diabetes, discuss your health with a doctor before exercising.

Pushing the body beyond its endurance also can induce nausea, according to the National Safety Council. Overexertion can occur while lifting heavy objects, performing aerobic exercises or walking on stairs, if the body is not accustomed to the activity, particularly after an illness or surgery. Come back slowly after a long layoff from vigorous exercise, working out at low intensity for short periods. When strength and endurance return, higher levels of exercise can be sustained without fatigue and nausea.