Bainbridge was born in Stockton, the son of a chemist. After Cambridge and a successful spell at several London hospitals, he became Professor of Physiology at Durham in 1911. His success was immediate and a chair of physiology was created at St Bartholomew's Hospital, which he occupied until his untimely death.
Bainbridge was a brilliant experimenter and his contributions to physiological science were of lasting value. Chief among them were his work on the mechanism of lymph formation, on urinary secretion, the effect of partial kidney removal, and above all, his studies on the circulation of the blood. His monograph The Physiology of Muscular Exercise (1919) is a masterly review of the subject.