Some of it is person dependent, but it's not the muscles that generally get injured. The things that tend to deteriorate are the joints, cartilage and bursa. These wear down over time, and can lead to injuries.

Every sport/activity when practiced for a long time has its own "signature" injuries due to long time, repetitive motion. Golf, for example, has a long history of lower back injuries in later careers, due to the continued rotation under stress. Swimmers have shoulder problems, tennis/pitches have elbow problems, etc etc.

There are certainly acute injuries that occur, but the chronic and overuse/long time injuries are just due to the same wear and tear over and over. You can think of it as a hinge that gets opened and closed many many times, eventually the pieces just wear out.