Cardio is a staple in any well-rounded fitness routine, including those designed by Nielsen Fitness in-home or virtual personal trainers. It gets the heart pumping, the blood flowing, and can seriously boost endurance — not to mention mood and energy levels.

That said, if you’ve ever been hit with an unexpected stomach cramp mid-run or during a workout, you’re not alone. These sharp, uncomfortable cramps can be frustrating and even derail your session altogether. A better understanding of why they happen, what causes them, and how to prevent them can help you enjoy your cardio with less painful interruptions.

WHAT CAUSES STOMACH CRAMPS?

Stomach cramps during cardio can stem from a few different places. The most common culprit is a side stitch, which is a sharp pain felt on either side of your abdomen, usually just below the ribs. “While the exact cause of side stitches is unknown, some theories suggest it could be related to blood flow to the liver, spasms in the diaphragm, or stretching of the ligaments” (Very Well Fit, 2024).

Your diaphragm — the muscle that helps you breathe — can sometimes become irritated during high-impact or intense cardio. This paired with irregular breathing can put extra pressure on the diaphragm and nearby ligaments, leading to cramping.

Another common cause of stomach cramps is poor digestion. If you eat too soon before your workout or choose foods that are hard to digest, your body might struggle to manage both digestion and physical exertion at the same time. This is because cardio pulls blood flow away from the digestive system and toward your muscles. If your stomach is still busy breaking down food, that competition for resources can result in cramping, bloating, or nausea.

Dehydration and electrolyte imbalance may also be a factor. Sweating during cardio causes you to lose essential minerals like potassium, sodium, and magnesium. These minerals help regulate muscle function and hydration balance. If your body is running low on them, muscles may spasm more easily.

HOW BREATHING AFFECTS STOMACH CRAMPS

Improper breathing is a sneaky cause of stomach cramps during cardio. Many people unconsciously breathe shallowly or irregularly when exercising. Instead of strong consistent breaths, they take panicked inhales through the chest. This type of breathing puts more stress on the diaphragm and limits the amount of oxygen your body is getting, especially during high-intensity cardio sessions.

Breathing too shallowly can also cause a buildup of carbon dioxide, which can further stress your system and contribute to the feeling of a cramp. As in-home and virtual personal trainers, one of the first things we coach clients on is establishing a breathing rhythm, ideally in through the nose and out through the mouth.

“In general, it’s healthier to breathe through your nose instead of your mouth. That’s because nose breathing is more natural and helps your body effectively use the air you inhale” (Healthline, 2021). Whether you’re running or doing a home-based HIIT workout, keeping your breath steady and full helps prevent discomfort.

HOW CORE STRENGTH & POSTURE IMPACT CRAMPING

Another factor that can contribute to stomach cramps during cardio is poor core strength and posture. Weak core muscles can cause slouching or hunching during workouts, especially running. This poor alignment compresses the diaphragm and limits the amount of space your lungs have to expand. The more compressed and restricted your breathing becomes, the more likely you are to experience side cramps or abdominal tightness.

Our in-home personal trainers in Toronto, Collingwood, London, Hamilton, and Ottawa (and virtual personal trainers everywhere) can help identify any postural or core weaknesses that may be contributing to cramps, allowing you to move with more stability and breathe more efficiently.

OUR TIPS

One of the most effective strategies to prevent cramping is to establish a pre-workout routine that includes light stretching and deep breathing. Stretching the side body, especially the obliques, can help loosen any tension in the abdominal region and prepare your body for movement.

Pacing is also crucial. If you go out too hard, too fast — especially if you’re new to cardio or returning after a break — your body might not be ready to handle the demand. Gradually building intensity gives your muscles, lungs, and digestive system time to adapt, which can help prevent cramps.

When it comes to intake, a general rule of thumb is to wait at least 30 minutes after a snack before doing cardio, and even longer after a large meal. Foods that are high in fat, fiber, or protein take longer to digest and can be more likely to cause issues, so stick to simple, easily digestible carbs if you need a quick boost.

Hydration also plays a critical role, as being slightly dehydrated makes your muscles more prone to cramping. At the same time, drinking too much water right before or during your workout can also cause discomfort or a sloshing feeling that might trigger cramps. Finding your balance is key. Sip water steadily throughout the day and consider adding an electrolyte drink if you’re doing longer or more intense cardio sessions.

Lastly, working with an in-home or virtual personal trainer can make a big difference. A Nielsen Fitness trainer can customize your cardio plan based on your current fitness level, help you optimize your breathing technique, and guide you on what to eat and when. That level of personalized attention can help you avoid common mistakes that lead to stomach cramps and keep your workouts consistent and pain-free.

WHEN TO SEEK PROFESSIONAL HELP

Occasional cramps are typically nothing to worry about, but “if it happens frequently, or is accompanied by other troubling symptoms, it’s best to make an appointment with your health-care provider. Hernia, gallstones, kidney stones, Crohn’s disease and irritable bowel syndrome are just a few of the causes of stomach pain that could be exacerbated by exercise” (Livestrong, 2025).

FINAL WORDS

Cramps can be annoying, but they don’t have to derail your progress. With a better understanding of what causes them and a few practical strategies, you can avoid those mid-workout pains and focus on getting the most out of your cardio sessions. The more in tune you become with your body’s signals and needs, the more enjoyable and effective your cardio workouts will be.