When it comes to exercise, you get out what you put in. So, when you devote a lot of work, you expect fabulous results. But, sometimes, the results of a workout are far from what was expected.
From surprise orgasms to black toes, a number of strange things can happen to the body when put through its paces. These issues often occur when the exercise is intense, when it lasts a long time and is atypical -- running a marathon, for example.
Many of the problems stem from simple nutrient depletion, as the body uses up fuel to sustain a tough work out.
"When the body is stressed, it reroutes resources, such as blood flow, away from non-vital systems," said Dr. Michelle Wolcott, assistant professor and sports medicine specialist at the University of Colorado at Boulder. "Muscles, particularly the heart and leg muscles, use up all available nutrients and oxygen."
Because of this, loading up on electrolyte salts or carbohydrates for energy won't solve the problem, and a person can go into a state of hyponatremia, in which the body cannot even process any nutrients.
Marathon and long distance runners seem to endure the bulk of odd side effects from physical exertion, although almost any activity done to excess can have adverse effects, from weight lifting to sports.
In general, however, weird phenomena resulting from intense exercise are out of the ordinary. It is rare that the average gym-goer would experience these problems.
"It's a distinct minority [of people] with a personality type that is probably very different," said Dr. Linn Goldberg, professor of medicine and head of the Division of Health Promotion and Sports Medicine at Oregon Health and Sciences University in Portland.
People who are adversely affected by a hard workout also often have underlying problems, such as a history of migraines, that make them susceptible to further issues.
Experts say the best way to exercise without side effects is to do it often, build intensity slowly and maintain proper nutrition.
"A little can be good, a lot does not mean it's better," Goldberg said.
The following is a list of some of the strange things that happen to the body during exercise.
Mystery or not, the female orgasm has an infinite capacity to surprise. The latest: orgasms making an appearance at the gym.
A phenomenon hotly debated on Internet message boards, many women claim to have orgasms while exercising, primarily during core muscle work, giving it the moniker "coregasm."
Crunches, hanging leg raises and other moves that tense and relax muscles surrounding the pelvis and the pelvic floor muscles seem to be the best triggers for coregasms.
"Orgasm is a physiological response," said Bean Robinson, associate director of the Program in Human Sexuality at the University of Minnesota Medical School. "We know some women who can have orgasms without any physical stimulation, just mental stimulation. ... It makes perfect sense to me that someone could have an orgasm [while exercising.]"
In addition, the pleasure hormones -- endorphin and dopamine -- that are released during exercise may contribute to coregasms.
But the phenomenon may still be rare enough to render the medical community skeptical. Few men have come forward with the same experience.
"I don't know of any science that supports that," said Dr. Ann Hoch, associate professor and director of the Women's Sports Medicine Program at the Medical College of Wisconsin.
Orgasm or not, good form is still important if women want physical benefits from their exercise program as well as other benefits.
Runners may enjoy many physical benefits from their exercise, such as a trim physique or great endurance. But pretty feet are not always part of the bargain.
"Runners tend to get black toe nails," said Dr. Lewis Maharam, medical director for the ING New York City Marathon and a columnist at runnersworld.com. "They can hurt and it's also embarrassing."
Black toes, known as subungual hematomas, occur when capillaries break and blood pools under the skin's surface. This often occurs in the toes because of the force of running or walking long distances. The problem is compounded if the runner is wearing shoes that are not big enough, causing the toes to constantly bang against the inside front of the shoe.
Though black toenails are unattractive and sometimes painful, they are not dangerous and will go away as the nail grows, though that can take as long as a year.
"I usually recommend wearing wider or longer shoes and running through it," Wolcott said.
Incontinence can be an embarrassing but common problem among long distance runners.
Often called runner's trots or runner's runs, the problem is essentially "increased diarrhea as you are running," Maharam said.
There are two reasons runners can experience diarrhea during a long race. First, the pounding, up-and-down movement of the body moves wastes faster in the gut. Second, at a certain exertion point, the body redistributes blood flow to better support the brain, heart and leg muscles, leaving the stomach, kidneys and other organs without as much support.
"Tissues break down with trauma, even mild trauma when it is repetitive," Goldberg said. "Muscles, tendons [and] blood vessel trauma occurs."
Reduced blood flow to non-vital organs also explains why people often can't stomach food following an intense workout and will throw up if they try to eat.
"Always stand to the side of a runner, never to the front," Maharam said.
There are ways to minimize the problem.
"It's as simple as what goes in goes out," Maharam said, and advised not to eat fatty foods, avoid fiber the morning of a race, and forget about carbohydrate loading the night before, unless that is part of a normal routine.
"Or else you are carb unloading at mile six," Maharam said.
"Women can exercise as much as they want, as long as they fuel their body appropriately," Hoch said, and that means plenty of calories.
It sounds like the ideal advice: eat, workout and be merry.
But not fueling enough can have serious consequences. And exercising too long and too hard without replenishing lost calories can keep many women from having a normal menstrual cycle.
In fact, without proper nutrition, the luteinizing hormone pulse responsible for kicking off ovulation -- the beginning of the menstrual cycle -- can be decreased. This results in missed periods and a body clock that is thrown off.
"You need that pulse in order to ovulate," Hoch said. "If you don't ovulate, you don't have a menstrual period."
Missing periods can also put women at risk for developing osteoporosis and cardiovascular problems. It seems counterintuitive that exercise can reduce bone density, but without nutrition and estrogen -- another hormone that can get depleted -- bones can become weak, even with physical activity.
Fitness proponents urge people to feel the burn and love the pain, but what if an exercise routine could actually kill you? For some, that fear can be a reality.
Exercise-induced anaphylaxis (EIA) is a condition in which, during physical exertion, the body's mast cells release histamine, the molecule responsible for the swelling and itching associated with an allergic reaction, according to a 1992 paper in the Clinical Journal of Sports Medicine.
People with EIA can have an allergic reaction, including hives, trouble breathing, nausea and wheezing, to even small amounts of exercise.
Dr. Thomas Casale, chief of allergy and immunology at Creighton University in Omaha, Neb., and executive vice president of the American Academy of Allergy, Asthma & Immunology, studied the phenomenon in the 1980s. He found that EIA is often associated with certain foods, such as celery, shellfish and peanuts that, when eaten on their own, pose no problem, but if eaten before a workout can trigger an allergic reaction.
Despite the seriousness of an anaphylactic reaction to exercise, small amounts of regular exercise can build the body's tolerance for physical activity. In addition, avoiding food triggers and using antihistamines can help those with EIA stick to their exercise regimes.
Think pumping extra iron or running 20 miles is uber-masculine? Think again.
"With shorter bouts of activity, hormones that strengthen us (like testosterone) can be increased," Goldberg said. "However, with excessive exercise, testosterone drops."
While hormonal imbalances due to excess exercise is not a huge problem, it can result in problems, including loss of bone density, decreased sex drive and feeling weaker or less energetic. Goldberg said this probably affects a small group of people with a specific, likely obsessive, personality type.
Lack of nutrients is the underlying problem of a hormonal imbalance as intense exercise can deplete the body of the raw materials necessary to make hormones.
Goldberg supposes the use of synthetic steroids can be a way to combat this imbalance.
"They depleted their own and they know it," he said.
Women can experience hormonal imbalances, as well, losing estrogen if they do not fuel themselves with calories during intense exercise, which puts them at risk for osteoporosis.
Sore muscles and aching feet after a workout is one thing. But a splitting headache is altogether different. And, for some, a bad headache is just part of their exercise routine.
"The physiology of exercise can promote the physiological changes in the brain that cause a migraine headache," said Dr. Joel Saper, founder and director of the Michigan Headache and Neurological Institute.
This can be true of almost any kind of physical exertion, from aerobic exercise to weight lifting to sex.
Beyond the exertion of exercise, straining muscles, particularly in the neck, are a classic trigger for a migraine or other headache. Pain in the neck muscles, joints and nerves can all translate to an intense headache.
But a post-workout headache can signal a more serious, even dangerous problem.
Too much or too little fluid in and around the brain can cause high-pressure or low-pressure headaches, respectively. These could signal spinal fluid blocks or leaks, which can be dangerous.
Increased blood pressure from exercise can, in rare cases, put someone at risk for aneurysms or intracranial bleeding.
But, Saper said, most of these headaches occur in people who are predisposed to headaches for some reason. If, for example, someone has a history of migraines or has low blood sugar because of diabetes, then they will be at risk for headaches after exercising.
"Common sense prevails on those kinds of things," said Saper, adding that if headaches are deemed benign by an expert, people can head them off by taking anti-migraine drugs or other pain medication.