Exercise-Induced Nausea: Why? How to Help It?

Exercise-induced nausea

Many people experience exercise-induced nausea and vomiting during heavy exertion. In the CrossFit gyms, they even put barrels for the contents of the visitors’ stomachs, and some even lose consciousness. It is difficult to call this phenomenon normal, but at least it is familiar to those who buy more than their first gym membership.

So, there can be several reasons for nausea and vomiting in the gym, and they can work in different combinations.

8 Reasons for Exercise-Induced Nausea

throwing up after workout
Typical bucket in CrossFit gyms

#1. Undigested food

Or a large volume of fluid in the stomach.

#2. Hyponatremia (drop in the concentration of sodium ions in the blood)

Due to the activity of the antidiuretic hormone, which regulates the balance of water in the body, water is retained by the kidneys, and water is redistributed from the blood plasma to the cells of the body. All this entails a sharp drop in the concentration of sodium ions in the blood plasma, which leads to nausea.

#3. Dehydration (lack of moisture in the body)

It occurs, among other things, due to an increase in body temperature and profuse sweating. On average, during high-intensity exercise, about 2-3% of body weight is lost, especially if the ambient temperature is quite high. A person begins to feel thirst, as a rule, when dehydration is 5%, but this feeling can be dulled by the action of catecholamines (this type of substance, in particular, adrenaline and dopamine, released during intense training). Dehydration leads to delayed gastric emptying, which in turn can lead to feelings of nausea when exercising.

#4. Overheating/heatstroke

During physical exercise, a person releases 15-20 times more heat energy than at rest, this is enough to raise the body temperature by 1 ° C every 5 minutes. At a certain level, the body is cooled by sweating. The main symptoms of heatstroke are complete collapse, confusion, nausea and vomiting, loss of consciousness, hypotension, and an increase in body temperature up to 40.5 ° C.

#5. Decreased blood flow to the gastric mucosa

Due to intense physical exertion, a decrease in blood flow to the central organs (intestines, liver) reaches almost 80% during exercise with an intensity of 70% of VO2 max (an indicator that characterizes the ability to absorb and assimilate oxygen from the air). In conditions of a lack of blood supply, the functioning of the gastrointestinal tract is disrupted, and the body tries to get rid of the contents of the stomach (in some cases, up to diarrhea).

#6. Increased penetration of toxins and allergens

Heavy physical exercise promotes the penetration of toxins and allergens into the intestines, due to the weakening of the protective barrier of the stomach and intestines (the barrier is formed by a complex combination of membranes, nodes, mucus, and immunological factors). It can cause inflammation, systemic gastrointestinal complications, including nausea, vomiting, bloating, bloody diarrhea, and cramping. Among the products that are dangerous for the penetration of toxins/allergens are cereals, seafood, peanuts, a variety of nuts, eggs, milk, and vegetables.

#7. Decrease in pressure

During leg training, a significant amount of blood rushes to the lower body, and blood flows out of the brain. In addition, blood vessels dilate, blood pressure decreases. Against this background, the effects of pressure on the area of ​​the carotid sinus (located in the area of ​​the carotid artery) can be observed, which activates special cells (pressure can also occur due to squeezing of the artery by the mechanism of blood pressure regulation), which give a signal to the brain about squeezing this site and trigger a nervous reaction, resulting in the heart rate is reduced, the blood arteries are dilated to relieve the resulting state of squeezing. All this also has an effect on lowering blood pressure.

After completing the exercise, in order to even out the balance, the body tries to redistribute the actively “gushing down” blood, constricts the blood vessels in the lower part and there is a sharp outflow of blood from the lower part to the upper part (and from the gastrointestinal tract as well), the heart still cannot cope with blood flow, tachycardia may appear, but at the same time, low blood pressure is also observed. Well, exercise-induced nausea, profuse sweating, dizziness, heart palpitations, epigastric discomfort, ringing in the ears are direct signs of low blood pressure.

#8. Rhabdomyolysis and other diseases may also cause exercise-induced nausea

Feel exercise-induced nausea? The cause of this condition may be rhabdomyolysis. Also, the reason for nausea are other diseases:

  • cholecystectomy, 
  • cardiac ischemia, 
  • pheochromocytoma, 
  • hypoglycemia.

How to Avoid Exercise-Induced Nausea

tired athlete

There is a quite obvious list of “DOs and DON’Ts”:

  • Do not eat abundantly before training. It is advisable to finish your meal at least an hour before exercise.
  • Perhaps you should exclude various pre-workout complexes from your diet.
  • Do not create a lake of water in the stomach, but at the same time do not allow dehydration of the body. It is necessary to drink during training – at least half a liter is recommended.
  • At the onset of the first signs of exercise-induced nausea (dizziness, increased sweating, cloudy eyes), it is necessary to interrupt the exercise and, ideally, lie or sit down.
  • After the symptoms have passed, continue with the exercise, possibly lowering the intensity. Over time, the body will adapt and the load will be easier to bear.
  • If exercise-induced nausea, etc. is observed against the background of deviations: rhabdomyolysis, cholecystectomy, cardiac ischemia, pheochromocytoma, hypoglycemia, then you need to consult a doctor.
  • With hypoglycemic signs: dizziness, weakness, trembling in the limbs, cold sweat, (possibly, but not necessarily) nausea, loss of consciousness, – you need to rest, sit down, eat some fast-digesting carbohydrates (a small chocolate bar, for example) or drink a cup of sweet tea. By the way, some people may have a special reaction to taking protein/carbohydrates before training, which can lead to hypoglycemic symptoms.

Sources About Exercise-Induced Nausea

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  6. Sinus node electrogram in patients with the hypersensitive carotid sinus syndrome | J Am Coll Cardiol. 1985 Jun;5(6):1484-90.| Gang ES, Oseran DS, Mandel WJ, Peter T.;
  7. Exercise-related syncope, when it’s not the heart | Clin Auton Res. 2004 Oct;14 Suppl 1:25-36.| Krediet CT, Wilde AA, Wieling W, Halliwill JR
  8. Postexercise hypotension. Key features, mechanisms, and clinical significance | Hypertension. 1993 Nov;22(5):653-64. | Kenney MJ, Seals DR.
  9. Cardiodynamic responses during seated and supine recovery from supramaximal exercise | Can J Appl Physiol. 1995 Mar;20(1):52-64. | Kilgour RD, Mansi JA, Williams PA
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