Why Do I Feel Sick After Working Out?

Introduction

You're halfway through your HIIT circuit and hit with a wave of nausea, or maybe you have to stop yourself from throwing up at the end of a run. Nausea after a workout is a common experience, and it can be a sign of pushing yourself too hard, not fuelling yourself properly, or dehydration. Rarely, certain medical conditions can induce this symptom.

If you can recognise what's causing your exercise-induced vomiting or nausea, you can change your routine to stop it from occurring in the future. Let's explore some of the common things causing you to feel sick while you exercise, and what you can do about them.

Causes of Exercise-Induced Nausea

Hydration

Most of us know how important it is to stay hydrated. Typically, an adult needs between 6-8 glasses of fluid a day, but this increases if you're losing more fluid than normal. It's easier to become dehydrated if you're sweating a lot, whether that's from exercising or because it's hot.

Exercise often leads to mild levels of dehydration due to sweating. When it's hot outside, it's common for athletes to lose between 2-6% of their body weight due to dehydration.

If you're dehydrated, it's common to feel or even be sick, which can heighten dehydration. Other signs of dehydration to look out for include:

• Feeling thirsty and/or a dry mouth

• Dark and/or strong-smelling urine

• Urinating less often

• Feeling tired or having no energy

• Dizziness or light-headedness

During exercise, you may feel overly tired, dizzy, or nauseous, or you may find your workout more challenging.

Rehydration is important (both during and after exercise) to avoid dehydration, but overhydration can lead to electrolyte imbalances and also trigger nausea and vomiting. When you sweat, you lose both water and sodium. Drinking too much water over a short period of time can dilute the sodium in your blood further, leading to an imbalance.

To avoid overhydration, try to space your drinking out over the day, taking small sips throughout, and opt for electrolyte drinks after intense exercise rather than just water.

Nutrition

Not eating enough, eating too much, or eating certain foods before a workout can all lead to that nauseous feeling during exercise.

Low blood sugar levels can make you feel hungry, nauseous, shaky, sweaty, and weak. This is more common in people with diabetes, but can also affect non diabetic people (especially after intense exercise). It's more common if you haven't eaten enough before working out and if you exercise for longer periods.

Eating small meals an hour or so before exercising can help you keep your blood sugar stable and reduce nausea. Some evidence suggests that eating fast-acting carbohydrates when exercising for 2 hours or more can help you avoid GI symptoms like nausea and vomiting. If you're diabetic, it's important to monitor your blood sugars regularly, eat carbohydrate-rich foods before working out, and always carry a fast-acting source of glucose such as a sugary drink or glucose gel.

The timing of the meal with regard to your workout can prevent you from feeling queasy. Eating too early may lead to feeling hungry again, and eating too close to the workout won't give your digestive system enough time to digest. Find out what works best for you in fueling your workout but limiting discomfort.

Slow-digesting foods, high in saturated fat, take longer to digest. This delay in digestion can lead to stomach fullness, a sluggish feeling, and maybe even nausea.

Whilst some people find vitamins and supplements can help fuel their workout, taking certain supplements on an empty stomach can lead to nausea. Some supplements, like iron, folate, vitamin C, and vitamin E, are worse than others. It's best to hold off on the supplements until you eat your first meal of the day (unless instructed otherwise by a healthcare professional).

Exercise Intensity

Sometimes it's the exercise itself that leads to you feeling nauseous. Very intense workouts lead to blood flow to your hard-working organs and away from the digestive organs. This can delay digestion and gastric emptying, leading to nausea after a workout.

Lower body workouts, in particular, engaging larger muscle groups on leg day workouts, may also make you more prone to nausea. Exercising too much or at too high an intensity can cause health issues if your body isn't used to it, so it's important to gradually increase the amount and intensity, listening to your body and ensuring you don't overdo it.

When it's hot outside, intense exercise increases the risk of heat exhaustion or heat stroke, so make sure to take things more slowly than usual and keep hydrated.

Symptoms Accompanying Exercise-Induced Nausea

Recognising Other Symptoms

Exercise can speed up how fast food passes through your digestive tract. If you notice you need to go to the toilet immediately after exercising, or that you experience diarrhoea after exercising, this isn't necessarily a problem. It's a normal bodily response to exercise.

Nausea can be unpleasant, but it is not normally an indication of an underlying issue. If however, accompanied by other symptoms such as stomach pain, chest pain, heart palpitations, severe shortness of breath/gasping for air, a headache, or dizziness, stop exercising immediately. These symptoms may signal a serious health condition that requires medical attention.

When to Seek Medical Care

If nausea after a workout is persistent, severe or occurs with other concerning symptoms such as chest pain, shortness of breath, fainting, a severe headache/vision disturbances, confusion or a rapid/irregular heartbeat, you should stop exercising and seek emergency medical help. These may be signs of an underlying medical condition requiring prompt attention.

Nausea with excessive sweating, high temperature, tiredness, a headache, thirst, and muscle cramps can be a sign of heat exhaustion. Heat exhaustion doesn't always need medical care if you can cool yourself down within 30 minutes, but if you experience the following signs, it's important to seek emergency medical attention:

• Confusion or loss of consciousness

• Fast breathing at rest

• A fast heart rate at rest

• Seizures

• Hot or red skin without sweating

Prevention Strategies

Hydration Strategies

It's best to drink 2-3 litres of water spread throughout the whole day rather than drinking lots of water prior to working out. However, drinking 400-600ml in the 1-2 hours before a workout can help to offset dehydration caused by exercise.

When working out, aim to replace fluids at the same rate that you're sweating. Read more details on how to calculate your sweat rate here, but the average sweat rate is between 1 and 1.5 litres an hour during exercise. For many people, this means drinking a litre of fluid for every hour of exercise.

Try to drink your fluid throughout the exercise session, as drinking in one go may lead to an upset stomach in some people. If exercising for more than 90 minutes, your fluids should contain some kind of carbohydrate to keep your blood sugar levels stable and fuel your body. Including electrolytes like sodium in your drink helps replace the electrolytes lost in your sweat and can help with hydration levels.

Continue rehydrating yourself after you finish exercising, aiming to drink 1.5 times as much fluid as you lost. Make sure to eat a balanced meal to replace the lost electrolytes and restore your body to its normal hydration level.

Nutrition Strategies

Fuel up on food three or more hours before working out with a balanced meal that includes lean protein and wholegrain carbohydrates. Higher fibre carbohydrates release their energy more slowly, so they are great for long workouts.

Around an hour before exercising is a good time for a small snack that includes some carbohydrates but is easy to digest. This should help to avoid feeling nauseous due to an overly full stomach, but give your body enough energy to work hard. Good snacks can include a banana, smoothie, or dried fruit.

If you're exercising for more than 90 minutes, it's best to refuel with a carbohydrate source like dates and other dried fruits or glucose gel.

After your workout, it's time to replace the energy and electrolytes you've used up. Try to eat a meal that includes both protein and carbohydrate-rich foods in the two hours after working out.

Avoid drinking alcohol or overly spicy food before working out, as this can lead to heartburn and nausea.

Managing Exercise Intensity

Taking things too intensely, too quickly, is a sure way to push your body too far. Build up the intensity and duration of your exercise programme as you become more accustomed to working out.

Aim to include a variety of different exercises and avoid types that you know make you feel sick, like exercises that compress your stomach or involve bouncing your body up and down.

When your body overheats, you're more likely to feel sick. If you feel yourself overheating, make sure to take a break. Don't forget to cool down properly at the end of your workout.

Summary

Whilst it's common to feel sick after an intense workout, if you're regularly feeling nauseous, you may need to take things more slowly. Make sure you're properly fueled and adequately hydrated before getting started. Drink regularly throughout your workout, and make sure you're fuelling your body with the right nutrients before and afterwards.

Remember to always listen to your body and adjust your workouts as required.