Nausea during exercise? Here's why some people feel sick during workout

Most people want to leave the gym feeling refreshed. For many, though, exercise is punctuated by this unpleasant sensation - a fleeting wave of nausea.

It can occur before starting the activity, during a difficult aerobic workout, or even when you are lifting heavy weights. And while it may be temporary, it’s your body’s way of telling you something isn’t right.

A common but often overlooked problem

Many people don’t realise how common exercise-induced nausea is. A review published in Sports Medicine says common causes of gastrointestinal problems following exercise include reduced blood flow to the digestive tract, dehydration, heat or very intense exertion.

These feelings can be experienced by anyone who pushes themselves beyond their body’s capabilities, but it’s endurance athletes who report them the most.

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“Many people think that they are unfit but it is actually the normal response of the body to exercise in some circumstances,” says Dr Sanjay Raina, Head of Internal Medicine, Amrita Hospital, Faridabad.

“The problem is usually with meal timings, hydration, intensity of workout, environmental factors and not some serious illness.”

What happens inside the body?

One of the primary reasons is the redistribution of blood to the body during activity. Instead of aiding digestion, blood is diverted to the muscles, heart and skin to meet the increased demand for oxygen and cooling.

When digestion slows, the stomach becomes more sensitive and you are more likely to feel nauseous.

According to Dr Raina, many cases are linked to factors such as meal timings, hydration levels and workout intensity rather than an underlying medical condition.

The role of food and meal timing

Another frequent cause is having a big lunch just before you exercise. High-fat or high-protein foods stay in the stomach longer.

One to two hours after such a meal, having an intense workout can cause bloating and nausea.

But working out on an empty stomach can sometimes be a challenge. Low blood glucose can cause weakness, dizziness, sweating and nausea.

Dr Raina says the issue is often not the exercise itself, but how and when people fuel their bodies before a workout.

Why hydration matters

Staying hydrated is another important factor. Even mild dehydration decreases blood volume, making it harder for the body to regulate body temperature during exercise, says the American College of Sports Medicine.

This can affect performance and increase the chances of fatigue, nausea and vertigo. These symptoms are especially common in hot and humid weather.

High-intensity workouts can trigger nausea

Special care should be taken with high-intensity exercises. Sprint intervals, hard squats, deadlifts and HIIT programmes all put the body under great strain.

Even healthy people can get sick during or just after exercise. Metabolic waste products build up quickly and blood flow to the stomach decreases.

“Sip water throughout the day instead of right before, eat a modest, high-carb snack one to three hours before you work out, and gradually increase the intensity of your workout,” says Dr Raina.

He adds that nausea can be avoided with just a few simple tweaks.

Listen to your body

Most importantly, don’t ignore discomfort - listen to your body.

Dr Raina also warns against ignoring severe or persistent nausea.

“Nausea, especially when accompanied by chest pain, fainting, severe vomiting, breathlessness or persistent despite lifestyle modifications requires assessment to rule out an underlying cardiac, metabolic or gastrointestinal condition.”

Simple changes can help

Fortunately, most people can avoid nausea during exercise.

Good hydration, smarter food choices, proper recovery and moderate training development can often keep both performance and stomach happy.

As Dr Raina points out, for many people, simple adjustments to hydration, nutrition and workout intensity may be all that is needed to prevent exercise-induced nausea.