Why Do You Feel Nauseous After All-Out Exercise?

Have you ever been to a HIIT class where you reach the end and fall to your knees, wanting to (or worse, needing), to vomit?

Bringing up your lunch is a common occurrence during max intensity efforts, but the reasons behind why such efforts make your stomach turn is still bit of a mystery.

This phenomenon is known as exercise-induced nausea, and you don’t need to panic – because it’s totally normal to experience.


A common misconception is that being nauseous during or after exercise means you’re out of shape – this is far from the truth.

Whether you’re a beginner, Olympian or endurance athlete, exercise-induced nausea can affect you. A studied examined twelve participants and found that exercise causes nausea, the severity of which is related to exercise intensity and food intake, but not sex differences nor physical training.

So, if your fitness level isn’t the cause, what is?


Exercise is designed to push us to the limits. During intense activity, many things can happen in your body that might result in vomiting.

Physiologically speaking, scientists suspect the nausea itself may be a product of lactic acidosis—when your blood becomes more acidic than your body can handle from accumulating levels of lactic acid during exercise. Other types of acidosis are known to cause nausea, and a decrease in blood pH can precipitate vomiting, as a way to regulate the body’s acid-base balance.

Lactate is used to create more energy, but if your muscles produce more lactate than they can handle, it accumulates in your blood. At a certain point, you reach the maximum amount of lactate your body can handle. This is called the lactate threshold.

As lactate levels increase, acidity levels also rise in your body. Your brain senses this as a toxic environment, and as a defense mechanism, it wants to get rid of the toxicity by causing you to vomit.

When this occurs depends on your conditioning and type of activity. If you suddenly do a crazy intense workout that might be beyond your ability, there’s a decent chance you might feel nauseous. Even a short break from training can cause unexpected nausea.


Considered the more prominent factor in whether you’ll experience nausea is what and when you ate ahead of your workout, and because your muscles do a ton of work during exercise.

To anticipate this your body focuses on your muscles, so they have the resources needed to help you perform at your best. In this case, the resource is blood, which carries oxygen and nutrients to your muscles.

To supply your muscles with extra blood, your body shifts blood flow away from your stomach and intestines, which slows down digestion. If you ate a poorly timed meal before starting an activity, the food just sits there causing an upset stomach. At a certain point, your stomach might reject the food and you will feel nauseous, or worse, vomit.

A 2001 study confirmed that eating a meal immediately before a high-intensity workout increases exercise-induced nausea – which isn’t surprising. But it most commonly occurs during full-body workouts.

When you use several muscle groups, more blood pools in your muscles and won’t be available for your stomach and intestines. You might also experience higher levels of nausea from leg workouts, because the muscles are so large.


People may be able to take steps to reduce or prevent nausea when exercising. These include:

  • Eating a diet with adequate fiber to maintain gut health but avoiding foods high in fiber before exercising
  • Avoiding slow-digesting foods, such as protein, fat, and milk products, before exercising to ensure quicker gastric emptying
  • Refraining from consuming foods and drinks high in fructose, particularly high fructose beverages, unless they also contain glucose
  • Staying well-hydrated before and during exercise to avoid dehydration, which can worsen gi symptoms
  • Consuming carbohydrate-rich foods with a higher water content or drinks with a lower carbohydrate concentration

A person can experiment with nutrition plans to determine which foods and drinks suit them best when exercising and how much time they need to leave between eating and exercising.

People may also find that it helps to warm up and cool down properly before and after exercising. Beginning with lower intensity workouts and gradually building up is also a sensible approach.

Want to take your training to the next level?

An Accredited Exercise Professional can assist you by guiding you through an individualized, safe and evidence-based exercise program to “bulletproof” your workouts. Get in touch with your local exercise expert today by clicking here.

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We have partnered with Nike Australia Pty Ltd for this article series.

The views expressed in this article, unless otherwise cited, are exclusively those of the author, Exercise & Sports Science Australia (ESSA). ESSA is a professional organisation committed to establishing, promoting and defending the career paths of tertiary trained exercise and sports science practitioners.

Nike had no role in the collection, analysis, or interpretation of data or research or the writing of this article.