Bronny James, the eldest son of basketball great LeBron James, is in a stable condition after suffering a cardiac arrest, a spokesperson for the family said.
A statement to ESPN said the 18-year-old was training with the University of Southern California (USC) basketball team when the incident happened.
"Medical staff was able to treat Bronny and take him to the hospital," it read.
"He is now in stable condition and no longer in ICU (intensive care unit)."
It added: "We ask for respect and privacy for the James family and we will update media when there is more information.
"LeBron and [his wife] Savannah wish to publicly send their deepest thanks and appreciation to the USC medical and athletic staff for their incredible work and dedication to the safety of their athletes."
NBA legend Magic Johnson said "we are praying and hoping he makes a full and speedy recovery".
