Dizzy after exercise

Originally Published: April 18, 2003 - Last Updated / Reviewed On: February 21, 2014
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Dear Alice,

Sometimes after jogging a while, or cycling a great distance, my head begins to spin and I feel as if I'm going to pass out. Is it normal to have feelings like these, and if so, how intense should these feelings be?

P.S.: your forum is a very helpful resource when a problem occurs in my life. Thank you for your continuing, inspiring, helpful answers to a lot of life's little (and some not so little) questions.

Dear Reader,

And thanks to you and everyone else for asking the questions.

Feeling lightheaded and/or dizzy, as if you are about to pass out, are not normal reactions to exercise. After an aerobic exercise session, you should feel invigorated, not totally wiped out. Your description sounds as though you are working extraordinarily hard. Do you eat anything before your physical activity? Are you drinking during your run or bike ride? How is your overall fluid intake? Although an exact diagnosis based on your description can't be given here, these few suggestions may help avoid these feelings:

  • Eat a snack prior to exercise. If you have less than one hour before your session, fewer than 200 calories is recommended. A piece of fruit and a couple of crackers work well for many people. Your snack can be a bit larger if you have two hours or so until your workout begins: one small plain bagel with jam, a piece of fruit and a yogurt, or handful of nuts and some crackers are a few suggestions.
  • Drink 16 oz. of fluid two hours before an event. This promotes hydration and allows enough time to excrete any excess liquid.
  • Drink fluids during exercise. Weighing yourself before and after exercise can help determine your sweat rate, and how much you'll need to drink.
    • If you lose 1 lb. per hour: drink 4 oz. every 15 min
    • If you lose 2 lbs. per hour: drink 8 oz. every 15 min
    • If you lose 3 lbs. per hour: drink 8 oz. every 10 min.
    • If you lose 4 lbs. per hour: drink 10 oz. every 10 min.
  • If you are exercising for longer than 60 minutes, add some fuel to your water with a sports drink. These fluid replacement drinks include glucose and electrolytes (sodium and potassium) to help with fluid intake and absorption.

Talking with your health care provider is a good idea if these strategies don't help. Being properly fed and hydrated, as well as getting enough rest and watching your breathing as your exercise, should help make your workouts more productive.

Alice