Why Do I Feel Faint When I Work Out?
Exercise What's inside?
Morgan Medeiros MSc
June 12, 2017

Feel Faint When I Work OutYour workout is going great when suddenly- uhoh: racing heart, tunnel vision, cold sweat, and shaky knees. If you’ve ever felt faint (or actually passed out) during a workout, you know how scary and demoralizing the experience can be.

While episode of faintness are not uncommon, many exercisers remain paralyzed to return to the gym after an episode. If you’ve ever felt shaky or gotten the spins during a workout, the following culprits may be to blame.

Heart issues

While most faintness, dizziness, or nausea during exercise is benign, there are certain cases in which the symptoms may be indicative of a more serious problem. In general, if you have a preexisting heart condition, high blood pressure, high cholesterol, prediabetes, Type II diabetes, or are more than 50 lbs overweight, you should always discuss an appropriate exercise routine with your doctor prior to engaging in an exercise regimen.

Occasionally, faintness, dizziness, nausea, a racing heart, or pain or discomfort in your chest may be indicative of a heart issue. If you experience these issues regularly upon exertion, you should speak with your doctor immediately.

Low blood pressure

Occasionally, a quick decrease in blood pressure may cause shakiness, dizziness, and/or fainting.

During exercise, the body increases blood flow to working muscles, temporarily reducing blood flow to the brain. This can, in turn, cause dizziness or a fainting spell. This may occur if you haven’t exercised in some time, although the occasional dizzy spell is just as common in active, fit individuals, thanks to a phenomenon known as EAPH, or Exercise Associated Postural Hypotension.

EAPH may happen at any time, but is especially common upon standing from a prone position: if you have ever experienced a bout of dizziness upon standing up, you have experienced the quick drop in blood pressure indicative of EAPH. EAPH often occurs in the hours or days following heavy exercise, as the body directs blood to tired extremities (such as the legs, after a long run or treadmill session) to enhance recovery and repair taxed tissues.

Reaching your cardiovascular threshold

Trying to do too much too soon- or pushing too hard (for example, while striving for a PR)- can cause dizziness, nausea, vomiting, and/or fainting. Sprints, heavy lifts, and other high-intensity exercises direct blood to the extremities and away from the brain, causing you to feel faint. In other instances, pushing too hard can cause lactate to build up in the blood, causing you to vomit.

In whatever instance, pushing to the point of nausea, dizziness, or fainting is by no means beneficial, necessary, or healthy, despite what many “warrior-style” workout fads might have you believe. If a trainer, workout buddy, or other gym member ever pushes you to exercise to such extreme levels, find a new workout partner.


Dehydration occurs during exercise when the body is losing more fluid (through sweat and/or respiration) than it is taking in.
Dehydration is not uncommon, and is rarely dangerous. Mild to moderate dehydration occurs regularly in novice exercisers, or those just returning to exercise after a hiatus. It takes time and experience to known when to hydrate, and how to recognize the signs of dehydration.

While mild to moderate dehydration is by no means beneficial or healthy, it typically isn’t of risk, as most adults will consume enough fluids and electrolytes to maintain within a safe range within a reasonable period of time following a period of mild to moderate dehydration.

However, in certain instances, dehydration can be life threatening (during long bouts of exercise, such as marathons, or during extremely hot conditions). The more dehydrated you are, the greater the risk for serious and adverse health effects. Always be sure to hydrate adequately during exercise, and take extra precautions if you are pregnant, have a preexisting condition, or are prone to overheating.

While you needn’t chug water or sports drinks (which are rarely necessary, except under the aforementioned extreme circumstances), you should aim to consume 9-24 ounces of fluid every 60 minutes, dependent upon body size and thirst.


Overheating often occurs alongside dehydration. In gyms lacking air conditioning (or while exercising in uncontrolled temperatures), it’s not uncommon for the heat to take its toll. The body works to regulate body heat, and while exercising, the body is generating additional heat, making the regulation process difficult. This is especially true during long periods of cardiovascular exercise, as greater fluid losses increase the risk for overheating.

Certain fitness classes (including hot yoga and spin classes) also increase the risk for dehydration, thanks to high temperatures (hot yoga) and high intensity (spin).

If you are prone to overheating, always exercise in an air-conditioned space, or invest in a cooling device, such as a specialized cooling bandana. Always be sure to hydrate, which reduces risk of overheating.

Feeling Faint or Dizzy? Quick Fixes:

Upon feeling dizzy, you should reduce exercise intensity immediately, but try to keep moving at a slow pace if possible, as stopping entirely may increase the risk for fainting by causing blood to pool in your extremities. Staying moving, albeit slowly, can help resume normal circulation, with blood returning to the brain and potentially reducing faintness and/or dizziness.

If you feel very faint, request assistance sitting down and putting your head between your knees, or lay down with your legs propped up on a wall or chair.

Drink small amounts of water and make sure you are within eyesight of another person who may be of assistance in case you do lose consciousness. Don’t be embarrassed to ask a gym staff member, trainer, or fellow exerciser for assistance. Gyms are trained to deal with situations that arise during exercise, and you will not be the first person to need assistance during a dizzy spell. If dizziness, faintness, or other symptom persists, contact a doctor immediately.

Morgan Medeiros is a certified nutritionist, holding a both a Bachelor and Master’s Degree in Clinical Nutrition. Morgan completed her undergraduate education at Central Washington University, and her graduate education at Northeastern University. During her time as a graduate student, Morgan focused her area of expertise in health education, weight management, and behavioral change. Morgan has experience working in areas of nutritional neuroscience and disease prevention, obesity prevention, and weight loss. Morgan also works in areas of nutritional analysis and menu labeling for restaurants, where she is able to creatively bridge her interest in food culture and health education. In her free time, Morgan enjoys traveling, reading, writing, running, and spending time with her family and friends (including- most importantly- her dog, Clyde).


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