Feeling Sick After a Workout? Causes and Simple Fixes

You finish the last round, stand up, and your stomach turns. You feel clammy, a bit shaky and you are not sure whether you need to sit down or find a bathroom. Feeling sick after a workout is something I see fairly often, especially with parents who are coming back to exercise after a long break, training on an empty stomach at 6am, or squeezing in a session straight after a rushed lunch. The good news is that most of the time it is down to a few common, fixable things.

This post explains the usual reasons, how to prevent it, and the signs that mean you should stop and get medical advice instead.

This is general information, not medical advice. If you have a health condition, are pregnant or are taking medication, check with your GP before starting or changing exercise.

Why am I feeling sick after a workout?

Here are the reasons I see most often in my classes in Archway.

1. You went too hard, too soon

This is the big one. When you suddenly push to a very high intensity, your body sends more blood to your working muscles and less to your stomach. If you are not used to it, the result can be nausea. It often happens in someone’s first class or first HIIT session in years, especially if they try to keep up with the fittest person in the room.

2. Eating too much or too close to training

A big meal, a greasy breakfast or a large milky coffee less than an hour before exercise can sit heavily in your stomach. Jumping and running movements make it worse.

3. Training on an empty stomach

The opposite problem. If you have had nothing since dinner the night before and then do an intense morning session, some people feel faint, shaky and queasy. This is common for parents who grab a coffee and go.

4. Not drinking enough, or drinking too much at once

Being dehydrated can make you feel dizzy and sick, and the NHS lists feeling dizzy or lightheaded among the signs of dehydration. But gulping a whole bottle of water in one go mid-workout can also slosh around and make you feel worse. Small, regular sips are better.

5. Stopping suddenly

Finishing a hard set of burpees and immediately lying flat on the floor, or standing completely still, can make you feel lightheaded and sick. Your heart is still pumping hard and blood is still in your legs. A gradual cool-down helps your body settle.

6. Heat and stuffy rooms

Training in a hot, airless room, or in a heavy hoodie, makes nausea more likely. Fresh air helps a lot.

7. Nerves

Anxiety about a new class or a hard session can upset your stomach before you have even started. That is normal, and it usually settles after the first couple of sessions.

How to stop feeling sick after exercise

Here is a simple checklist I give to new clients:

1. Time your food. Aim for a normal meal 2 to 3 hours before, or a small snack like a banana, a slice of toast or a yoghurt 30 to 60 minutes before. My guide to what to eat before a bootcamp class has more ideas.
2. Do not train completely empty if you are prone to feeling shaky. Even half a banana helps.
3. Drink regularly through the day and take small sips during the session, rather than downing a bottle at once.
4. Warm up properly. Five to ten minutes of easier movement lets your heart rate rise gradually. See my warm-up before exercise guide.
5. Build intensity over weeks, not minutes. In your first few sessions, work at a level where you could still talk in short sentences.
6. Cool down. Walk around slowly for 3 to 5 minutes after the hard part. Do not lie flat straight away.
7. Dress light and get air. Open a window at home, or step outside for a minute after class.
8. Go easy on caffeine before training if you notice it upsets your stomach.

What to do if you feel sick during or after a workout

• Stop or slow right down. Do not try to “push through”.
• Walk slowly or sit down with your head up. If you feel faint, sit with your head between your knees or lie down with your legs raised.
• Take small sips of cool water.
• Get some fresh air.
• Once you feel better, have a small snack.

The NHS page on feeling sick (nausea) also suggests fresh air, regular sips of a cold drink and smaller, more frequent meals.

When feeling sick after a workout needs medical advice

Most post-exercise nausea passes within 15 to 30 minutes. But please do not ignore these signs.

Call 999 straight away if feeling sick comes with chest pain or tightness, pain spreading to your arms, back, neck or jaw, or shortness of breath. The NHS lists this combination as a possible sign of a heart attack.

Speak to your GP if:

• You feel sick after almost every session, even gentle ones.
• The nausea lasts for hours or keeps coming back over several days.
• You also have palpitations, fainting, unusual breathlessness or dizziness that does not settle.
• You have a heart condition, diabetes or high blood pressure, or have recently started new medication.

If you cannot get through to your GP, you can call 111.

Where a bootcamp class fits

A lot of people feel sick in their first class because they try to match everyone else. In my sessions, every exercise has an easier and harder version, and I would much rather you finish feeling good than finish on the floor. If you are nervous about how tough it will be, read how hard is a bootcamp class. The SYP Recharge energy and focus class is a great first choice: steady intervals designed to leave you feeling better, not worse.

FAQs

Is it normal to feel sick after a hard workout?

It is common, particularly when you are new to exercise or have pushed much harder than usual. It is not a sign of a good workout, though. It usually means the intensity or timing of your food needs adjusting.

How long does nausea after exercise last?

Usually 15 to 30 minutes once you stop and cool down. If it lasts much longer or keeps returning, speak to your GP.

Should I eat if I feel sick after exercising?

Wait until the nausea passes, then try something small and plain, like toast, a banana or crackers, with sips of water.

Can dehydration make you feel sick after exercise?

Yes. Dehydration can cause dizziness, tiredness and nausea. Drink regularly through the day, not just during your workout.

Book your first class

If you want to get fitter at a pace that suits your body, come and try a class. SYP Bootcamp runs 45-minute small-group sessions in an indoor church hall in Archway N19, max 10 people, £15 a class, for every fitness level. Book your £15 class here or call or WhatsApp me on 07301 512215 and I will send you the timetable. If you want a slower, fully personal start, see how my 1-1 personal training works.

About the author

Artem Olekhnovych is a personal trainer in Archway and the founder of SYP Fitness and SYP Bootcamp. He has coached clients in Archway, Highgate and across North London for over 10 years, and runs small-group bootcamp classes for busy mums and dads. Read reviews from his 1-1 clients.