Has anyone ever noticed if certain muscles don't react like other muscles? For an example, I rarely focused heavy on my traps/shoulders. Since I have been training my traps and shoulders for quite some time now, I have noticed that my left trap and shoulder is developed better than my right side. The same goes for my pecs and biceps. It is not that noticeable but I notice it. My left side is getting bigger and more defined than my right side.

On the other hand, I am having an opposite affect on my lower body. My right leg and calf are developing better than my left leg and calf. Could this be due to injuries I suffered? I tore my right rotator cuff about 10 years ago. I did rehab and everything for it but I didn't get back into strength training until a year or so after the surgery due to pain and discomfort during exercises that worked basically any muscle group that was part of moving my shoulder (traps, back, pecs, biceps)

Basically the same scenario for my left leg. I blew out my ACL about 10 years ago and only rehabbed it. Didn't do strength training on my legs for close to 2 years.

Could this be some sort of atrophy? Is there a way to correct it?