Answer:
The answer to the question: Musicians must train their muscles to play instruments, just as athletes must train their muscles to play sports, is, false.
Step-by-step explanation:
Musicians do not necessarily need to develop muscle mass in order to be able to play an instrument, because what they need is agility to be able to play them and their mental capacity, as well as their hearing skills. Instruments are usually pretty light, easy to handle, therefore to play them a musician only needs the agility of his/her fingers and limbs and his mental and sensitive abilities. Athletes abilities and skills do depend entirely on muscle mass as the power of their body, whether the rough, or refined skills, depend on the perfection of their muscle capacity. This is why the statement would be false.