Why do I get dizzy after exercise?

Q:One of my New Year’s resolutions was to start exercising more often. It’s going great, except I sometimes get very dizzy when I finish a workout. What’s up?

A:Are you drinking plenty of water before and during your workout? If not, dehydration could be behind your dizziness. Most of us are diligent about downing water when it’s hot out, but our body’s thirst response is diminished by up to 40% in the winter, according to University of New Hampshire researchers. The reason? Our blood vessels constrict when the weather is cold to keep our core warm, but this also fools our body into thinking it’s hydrated, so we don’t feel thirsty. When exercising, make sure you have a water bottle handy, no matter the time of year. I advise sipping 4 to 16 oz. for every 15 to 20 minutes of exercise, and at least 64 oz. total throughout the day.

Another common cause of dizziness after exercise: low blood sugar, especially if you’re exercising before eating breakfast. The reason: When you eat, your body stores energy as glycogen to use between meals. But when you exercise before eating and use up all of your stored glycogen for energy, your body has no fuel left, which can cause dizziness. To avoid the issue, try having a light meal that includes complex carbohydrates, like whole-grain breads or cereal, before you exercise. Complex carbs turn to energy more slowly than simple carbs, like white bread, so they provide a longer energy boost. Plus, they won’t leave you feeling sluggish after eating.

If neither of these rid you of dizziness, you can try dialing back the intensity of your workouts, building back up gradually. But if the symptom persists, or is accompanied by palpitations, shortness of breath or chest tightness, I advise seeing your doctor.