An NYC Marathon runner died suddenly at 24. Her family says the cause was rhabdomyolysis, a rare risk that can even affect fit athletes.

A woman died after collapsing at the New York City Marathon from a rare side effect of hard exercise called rhabdomyolysis. kena betancur / AFP via Getty Images A New York City Marathon runner died after collapsing at the finish line near Mile 24. Her family said the cause of death was rhabdomyolysis, a rare side effect of hard exercise....