Blood reproduction rate
The blood reproduction rate was the rate at which one's body replenished its supply of blood.
In 2268, during a cyrogenic open-heart procedure, Nurse Christine Chapel reported Spock and Sarek's vital signs, including the fact that the former Vulcan's blood reproduction rate was up over 200%. Doctor Leonard McCoy then admitted he didn't know whether it was good news or bad. (TOS: "Journey to Babel")