By Sarah Joseph

For years, researchers and fitness pros have been touting the healthy side effects of exercise. Regular workouts can help you lose weight, boost you mood, and live a longer, more satisfying life. But your daily workout can also have some strange ~ and pretty wonderful ~ side effects. From exercise-induced ear popping to the, uh, pleasures of a core workout, your body can have some decidedly odd physical reactions.

Yawning

Nobody really knows for sure why we yawn, let alone why some people yawn excessively at the beginning of a workout. It may be that yawning is your body’s way of dealing with transitions, such as when you’re waking up, getting bored, or working out. “If you jump straight into a workout, your body is still adjusting to your change in breathing and blood vessel dilation. Yawning may be an indicator that you’re warming up,” says Alice Burron, MS, exercise physiologist and spokesperson for the American Council on Exercise.

Passing Gas

Nothing interrupts finding your Zen like hearing a loud rip in yoga class ~ or trying to hold one in yourself. It’s a bit embarrassing, but passing gas is actually quite common during yoga and other forms of core work, says Burron. Leg lifts, crunches, and other moves that target your belly and abs build pressure around your middle. Each time you contract the muscles around your internal organs, you up your chances of letting one loose.

Runny Nose

While some people report that their breathing clears up when they exercise, far more complain about getting a runny nose. “Exercise stimulates the part of your nervous system that controls the secretion of your body’s glands ~ including the mucus glands in your nose,” explains William Reisacher, MD, director of the Allergy Center at New York-Presbyterian/Weill Cornell Medical Center.

Running outside? That extra nasal drip may also be a reaction to pollen, the temperature, or outdoor humidity. In cold temperatures, your nose has to work harder at warming up the air, dilating your blood vessels and stimulating mucus production.

Ear Popping

Ear popping occurs because your body tries to maintain equal pressure between the outside air and that inside your middle ear. When there’s a sudden shift in air pressure ~ say, when you’re taking off in a plane or diving into a pool ~ your body adjusts by moving air through your Eustachian tube, the part of your ear that connects your middle ear to the back of your nose. “The same thing happens each time your foot strikes the ground or you do a heavy lift,” says Dr. Reisacher. “Your body braces for impact and pressure is generated and transmitted to your ear.”

Hives

For some people, being “allergic to exercise” isn’t merely an excuse to stay on the couch. In very rare instances (less than 0.5 percent), working out can cause exercise-induced anaphylaxis, an allergic reaction that can lead to hives, flushing, and wheezing. Just a moderate bout of exercise can cause an episode, but most reactions need a food trigger as well.

“Exercise increases the permeability of your GI tract and lets more partially digested foods get into your circulation,” says Lawrence B. Schwartz, MD, PhD, chair of the division of rheumatology, asthma, and immunology at Virginia Commonwealth University. That’s why you might have a reaction that you might not otherwise have had from eating the food alone.

Heartburn

Mid-run you’re overcome by a burning pain in your chest. But don’t worry ~ it’s likely just your morning breakfast burrito saying hello.

Certain kinds of exercise, such as running or sit-ups, can push your stomach contents up into your esophagus, resulting in acid reflux/heartburn, says Edgar Achkar, MD, vice-chairman of the Digestive Disease Institute at the Cleveland Clinic. It makes sense, then, that the more jarring the exercise, the more likely you’ll feel the burn.

Headache

Exercise can cause your heart and head to pound. As with yawning, no one knows for certain why exercise headaches happen, but researchers hypothesize that rigorous workouts cause the blood vessels inside your skull to dilate.

While anyone can experience an exercise-induced headache, it’s particularly common among men in their 20s. Part of this may be due to the fact that men are more likely to lift weights and perform moves that can store tension in the upper back, which can lead to a pounding head.

And we saved the best for last…

Coregasm

Here’s some extra motivation to exercise: A number of women report having an orgasm ~ or “coregasm” ~ while working out. But not just any fitness routine can trigger the big O. As the name suggests, coregasms most commonly happen during an intense core workout, which may explain the wait for the Ab Roller at the gym.

While any moderate physical activity can trigger the release of feel-good endorphins and increase your blood circulation, core workouts, in particular, target the same muscles that contract during orgasm. “When you’re doing Pilates or Kegel exercises, you’re working your PC and pelvic floor muscles,” says Sara Nasserzadeh, PhD, co-author of The Orgasm Answer Guide. “It’s probable that feel-good feeling you get from contracting your muscles during core exercises can mimic those generated during genital-stimulated orgasms.”

Suddenly, I feel like heading to the gym…