What does the average guy usually expect from a workout? Sweat, muscle failure, maybe a little pain from lactic acid buildup? Heck, you might even welcome them.

And sure, things like dizziness, heartburn, and a side stitch that stops you in your tracks, on the other hand, can definitely put a damper on exercise plans. But when do symptoms go from tough medicine to warning signs? And when does sucking it up get sidelined in favor of an actual doctor’s appointment?

Here, experts discuss weird workout side effects, what your body may be trying to tell you—and when you should actually start worrying.


After doing your usual squat routine, your trainer decides to mix in single-leg squats, and your first attempt makes your leg muscles shake as if you’ve been shot with a taser. What gives? It could be a number of things, says Keith Veselik, M.D., director of primary care at Loyola University Health System in Chicago. “Often muscles shakiness is simply due to fatigue. You’re likely pushing it to the point where you’re maxed out.”

Your blood sugar may also be low, says John P. Higgins, M.D., director of exercise physiology at the Ironman Sports Medicine Institute at Memorial Hermann-Texas Medical Center. Hypoglycemia (low blood glucose) can cause symptoms ranging from tremors to fatigue, and even loss of consciousness, says Higgins.

How to reduce your risk: Eat before you exercise to avoid a drop in blood sugar. Think protein and carbs, like whole-wheat toast with peanut butter or half of an energy bar, suggests Veselik. And if it lasts for longer than a few hours, see a doctor.


Clearly, hoisting 50-pound dumbbells over your face is not the time for a dizzy spell. And like the shakes, dizziness may be due to several different factors, says Veselik. Vertigo can occur when you’re leaning back and the room appears to spin, or significant dehydration can lead to a state called hypovolemia, or low blood volume, which may produce dizziness, says Higgins.

How to reduce your risk: Immediately stop working out and drink some water. Vertigo is likely an inner ear problem, says Veselik, and requires working with a physical therapist trained in vestibular therapy. If you’re a normal healthy guy and you feel unusually dizzy for a few minutes or longer, call a doctor. It may be a sign of a heart arrhythmia or other heart problem.


Contrary to what you see on The Biggest Loser, nausea during a workout is not normal, and it may be triggered by a number of different things. Eating the wrong food at the wrong time or pushing yourself too hard can all cause queasiness and even vomiting. “If you’re working out to that extent, back off and gradually acclimate to that intensity over time,” says Veselik. Nausea can also occur from taking vitamins on an empty stomach, says Higgins. “It’s more common with supplements high in iron, multivitamins with herbal additives, and those containing lots of fillers and binders.” Taking other medications at the same time as your vitamins, such as caffeine pills, may make it worse.

How to reduce your risk: Take vitamins with food, preferably at breakfast or lunch. And if you repeatedly suffer from nausea, you might want to void eating solid food three hours prior to a workout. For a more easily digestible, quick-energy alternative, try a liquid meal replacement that includes carb and protein about 30 to 60 minutes before you exercise.


Common sense tells you that guzzling a 20-ounce bottle of water isn’t a great idea before you do decline chest presses. “We all have a little physiological reflux, which is normal,” says Higgins, and even those who don’t usually have a problem with indigestion may experience some reflux or heartburn at the gym. Higgins warns that taking ibuprofen on an empty stomach may make symptoms worse, as will eating or drinking too close to your workout.

How to reduce your risk: Try taking small sips of water during your workout instead of big gulps, and wait an hour or two after you eat before working out. If the heartburn is accompanied by shortness of breath and/or chest pain, see a doctor immediately, as these may be symptoms of a heart attack.


Typically seen in runners, this stabbing pain in the side can come out of nowhere and literally take the wind out of your sails. It’s known as exercise-related transient abdominal pain (ETAP) in the medical world, and it’s surprisingly common. “A new exercise program or increasing the intensity of your current program seems to increase ETAP,” Higgins says. Several theories about ETAP exist, but posture appears to play a role, according to a 2010 study published in the Journal of Science Medicine and Sport. Slouching or running hunched over may affect nerves that run from the upper back to the abdomen, resulting in pain.

How to reduce your risk: Run using good posture and try adopting a rhythmic breathing pattern, which involves coordinating your breathing with your foot strikes, says Higgins. ETAP typically reduces with time and as overall fitness improves.

By Linda Melone, C.S.C.S