7 Signs You Should Stop Exercising Immediately

Anna Medaris Miller

Love your heart.

Ashley Langford is in tune with his body. The 40-year-old Web developer and photographer near Dallas, Texas, traded his party-hard lifestyle for intense exercise such as P90X and CrossFit in 2010. So when his heart rate "took off" from 140 to 180 beats per minute while on the rowing machine last year, he knew something was seriously wrong. But would you know the signs it's time to stop exercising immediately and head straight to the hospital?

Your heart (generally) hearts exercise.

Let's set one thing straight: Exercise is overwhelmingly good for your heart. "I never want to scare people off from exercising because, for most people, the benefits far outweigh the risks," says Emily Johnson, a clinical exercise physiologist at Washington State University. Physical activity is one of the most effective ways to ward off heart disease and stroke, two top causes of death in the U.S., according to the American Heart Association, which recommends at least 150 minutes of moderate exercise or 75 minutes of vigorous exercise each week.

Here's the caveat.

Still, more exercise and more intense exercise isn't always better, particularly for people with certain underlying heart conditions. "There is a little bit of this cardiac arrest paradox, where we're telling people, 'Exercise is beneficial when you do it on a regular basis, but at times, can be a trigger for something worse,'" says Dr. Jonathan Drezner, a family medicine physician at the University of Washington, who specializes in sports medicine. Here are seven of those times:

1. You haven't consulted your doctor.

If you're at risk for heart disease -- meaning you have hypertension, high cholesterol or diabetes; you smoke or have a family history of heart disease, heart attack or sudden death from a heart problem; or all of the above -- it's important you talk to your doctor before beginning an exercise plan, Drezner says. Young athletes should be screened for heart conditions, too. "The worst tragedy of all is sudden death on the playing field," says Drezner, whose work focuses on the prevention of sudden cardiac death in young athletes.

2. You go from zero to 100.

Ironically, out-of-shape people who can benefit most from exercise are also at higher risk for sudden heart problems while working out. That's why it's important to "pace yourself, don't do too much too soon and make sure you give your body time to rest between workouts," says Dr. Martha Gulati, editor-in-chief of CardioSmart, the American College of Cardiology's patient education initiative. Building up to more strenuous exercise also helps familiarize you with how your heart rate, sweat, fatigue level and body heat changes, Johnson adds. "It's important for people to keep the normal response in their minds so they know what's abnormal," she says.

3. You experience chest pain.

"Chest pain is never normal or expected," says Gulati, also division chief of cardiology at University of Arizona College of Medicine, who says that, in rare cases, exercise can cause a heart attack. If you feel chest pain or pressure -- especially alongside nausea, vomiting, dizziness, shortness of breath or extreme sweatiness -- stop working out immediately and call 911, Gulati advises.

4. You're suddenly short on breath.

If your breath doesn't quicken when you exercise, you're probably not working hard enough. But there's a difference between shortness of breath due to exercise and shortness of breath due to a potential heart attack, heart failure, exercise-induced asthma or another condition. "If there is an activity or level that you could do with ease and suddenly you get winded ... stop exercising and see your doctor," Gulati says.

5. You feel dizzy.

Most likely, you've pushed yourself too hard or didn't eat or drink enough before your workout. But if stopping for water or a snack doesn't help -- or if the lightheadedness is accompanied by profuse sweating, confusion or even fainting -- you might need emergency attention, Johnson says. "These symptoms could be a sign of dehydration, diabetes, a blood pressure problem or possibly a nervous system problem," she says. Dizziness could also signal a heart valve problem, Gulati says.

6. Your legs cramp.

Cramps seem innocent enough, but they're not to be ignored -- "especially in the legs," Johnson says. Leg cramps during exercise could signal intermittent claudication, or blockage of your leg's main artery, and warrant at least a talk with your doctor, she says.

7. Your heartbeat is wacky.

Langford, the Web developer in Texas, knew to go to the emergency room when he felt his heart race since he had been previously diagnosed with atrial fibrillation, an irregular heartbeat. Such conditions can feel like "fluttering or thumping in the chest" and require medical attention, Johnson says. In all, Langford underwent electrical cardioversion (a shock to the heart), two ablations (procedures that destroy the heart tissue causing the irregularity) and was put on medications. Now drug- and hospital-visit free for six months, he mountain bikes, kayaks and is even training for a half-marathon -- but he's steering clear of extremes like CrossFit. "I still haven't pushed the limits," Langford says, "but I'm happy with where I'm at."