Operators of the Morse instruments spent long periods tapping the key to send the coded messages along wires. On occasions in some offices, an operator would work for hours sending long (15,000 - 20,000 word) messages especially after an important event or speech. There was never a recognition of the underlying issue of the strain operators placed on their wrists and fingers in particular from their repetitive task.
One of the early articles which recognised the problem was printed by the Sydney Mail on 3 July 1875 which can be accessed here.