Rachel Apa, a former college field hockey player who had trained for months for her first marathon, died after collapsing about two miles from the finish of the New York City Marathon. Her father, Steve Apa, said she died of rhabdomyolysis, a condition in which damaged muscle tissue breaks down and releases substances into the bloodstream.

Apa had been exercising regularly and was in what her father described as excellent health. After passing the nine-mile point, she texted him that she felt amazing. He replied that she should take it easy, reminding her it was her first marathon.

Witnesses said Apa collapsed around mile 24 in Central Park. Three people, including two who said they were doctors, took turns performing CPR. New York Road Runners said medical staff used a defibrillator before paramedics took her to Mount Sinai Medical Center. She was pronounced dead after six hours of attempted life-saving measures.

Rhabdomyolysis, often called rhabdo, is relatively rare, with about 26,000 cases reported annually in the United States, according to the information provided. The National Institutes of Health describes it as the breakdown of skeletal muscle, which releases components such as myoglobin and electrolytes into the blood. These can affect the kidneys and may lead to acute kidney injury and other complications.

Crushing injuries are a common cause, but overexertion, severe dehydration and overheating can also trigger the condition. Certain medications, prolonged inactivity and some physical conditions are also cited as possible causes. Endurance athletes and people undertaking high-intensity activity are among those at greater risk, particularly when they push themselves beyond what they are accustomed to.

Symptoms can include muscle soreness or weakness, swelling and unusually dark or discolored urine. They may appear one to three days after a muscle injury, and persistent soreness can be difficult to distinguish from ordinary post-exercise discomfort.

Rhabdomyolysis can be treated, but prompt medical care is important. Treatment commonly involves intravenous fluids and monitoring of electrolyte levels; severe kidney damage may require dialysis.

Sources: E! News.