The feeling or sensation of being just about to pass out during your workout can come in the form of dizziness or lightheadedness.

“Dizziness and/or feeling lightheaded during exercise can be related to several issues,” says Teresa Caulin-Glaser, MD, a cardiologist and senior vice president with Service Lines, OhioHealth.

“The most common two causes are dehydration and low glucose (blood sugar) levels.

“Oftentimes individuals exercise on an empty stomach, and the glucose levels fall.

“This results in lightheadedness and sometimes confusion. Having a small snack can eliminate this problem.”

Gym Sessions

My underweight personal-training clients almost passed out during exercise because they probably hardly ate anything that entire day; that would have been very easy to believe, given their body weight status; thin and malnourished is NOT healthy.

Dr. Caulin-Glaser continues: “Dehydration is commonly seen in individuals exercising. Drinking fluids when you are exercising is important for a few reasons.

“There will be insensible loss of fluids from the body with exercising due to sweating.

“Also, blood vessels dilate with exercise and as a result blood pressure drops.

“The drop in blood pressure can last for several hours after exercise. The result can be lightheadedness.”

Additionally, feeling like you’re going to pass out while exercising is also a function of how physically fit you are in the first place.

My clients were under-exercised; not used to good hard workouts.

People in top physical condition can almost always hammer away at a workout session on an empty stomach without feeling ready to pass out.

Dr. Caulin-Glaser adds: “It is important to know that there can be cardiovascular reasons for lightheadedness and these need to be evaluated.

“The problems may be related to abnormal heart rhythms and/or structural heart problems.

“It is always important to speak to your physician about any new symptoms, I recommend regular evaluations with your primary care physician, especially if you are initiating a new vigorous exercise program.

“Your doctor may refer you for a cardiac evaluation based on your history and exam.”

If you’ve been cleared for any medical problems, but are still feeling like you’re on the verge of passing out during exercise, re-evaluate your eating and hydration habits.

Dr. Caulin-Glaser is an experienced physician, teacher and researcher in the specialty of cardiovascular disease, and formerly the system vice president for Heart & Vascular Services at OhioHealth.
Lorra Garrick has been covering medical, fitness and cybersecurity topics for many years, having written thousands of articles for print magazines and websites, including as a ghostwriter. She’s also a former ACE-certified personal trainer.


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