Pilates is intended to realign the body. With every focused breath and movement, the physical fitness system is supposed to help you achieve balance as you reach deep into your body's core.
But all one 59-year old woman found in her core was her right breast implant, which shifted when she engaged in a deep exhale.
The case of the pilates-session-turned-breast-disappearing act was published by Johns Hopkins' University emergency medicine doctors in the New England Journal of Medicine.
The woman, who had not been identified, had a history of breast cancer and had undergone a bilateral mastectomy and breast reconstruction.
But while forcefully exhaling while keeping her mouth closed and nose pinched shut -- called the Valsalva maneuver -- the woman lost her implant somewhere in her body.
"I remember her saying, 'My body swallowed my boob,'" Dr. Tiffany Fong, resident physician in the Department of Emergency Medicine at Johns Hopkins Hospital, told ABCNews.com.
An ultrasound performed in the emergency room helped doctors find the implant, which was lodged between the lower part of the woman's right lung and ribcage.
"When she would do the breathing maneuver, we saw a part of the chest bulge out," said Fong. "We found that it was a part of her lung that was protruding."
But for this woman, it didn't hurt as bad as it sounds, the emergency physicians wrote in the case report.
"She could've had a hard time breathing because it would've taken up space in her lungs," Dr. Gedge Rosson, director of breast reconstruction at Johns Hopkins Hospital, told ABCNews.com. Fortunately, she didn't.
More than 90,000 breast reconstruction procedures were performed in 2010, an 8 percent increase from the previous year, according to the American Society of Plastic Surgeons, and while there are many different types of reconstruction procedures, breast reconstruction surgery heals much like other surgeries.
The incision area should not be subjected to excessive force or motion during healing, according to the American Society of Plastic Surgeons.
Patients are often advised to wait about four to six weeks before exercising. The same waiting time recommendations apply for heart valve surgery, said Rosson.
The woman described had also undergone a procedure to repair one of her heart valves, which required surgeons to re-enter from the same incision used for her reconstruction operation. The heart valve procedure required surgeons to create a tiny incision between her ribs.
According to Rosson, the incision from the heart procedure, not the breast reconstruction, caused the implant to move out of place.
"It made a tiny enough opening to make the breast implant fall through," said Rosson. "If you just have breast reconstruction alone, this is highly unlikely."
Fong recalled that the woman participated in the Pilates session about three months after her surgery, which was outside the restriction window.
The surgeons retrieved the implant from her chest, repositioned it in its proper place, and sealed the internal incision with mesh.
This type of case is extremely rare, Fong said. She recalled finding only three similar reported cases of women who'd lost their breast implants.
"Whenever you have a surgical procedure like this, it creates an opening that's a source of weakness in the chest wall," said Fong. "And even after healing, it isn't going to be as strong as your native tissue."
But Rosson said this rare case shouldn't deter women from exercising after the recommended wait time is over, as exercise can help keep women who have undergone such procedures healthy and in good spirits, he said.
"Patients should really not be worried about having a breast reconstruction," said Rosson.