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One Arm Much Bigger (Not Due To Overcompensating)

I started lifting again about a little more than 3 months ago after 10 months off due to a bad/stubborn injury and noticed that my left arm is much bigger than my right and my left bicep has the vein popping out, but it’s nowhere to be seen on my right. I measured both arms and sure enough, my left arm is 3/4 of an inch bigger than my right. I never noticed this before, so a lot of it must have happened in these past 3 months. I’ve been going strong these past 3 months getting back into it. There was probably a difference before that, but it wasn’t noticeable at all. Everything that I’ve read is that this is common and that my strong arm is most likely overcompensating for my weak arm and to just increase the amount of reps on the weaker one until it catches up. This doesn’t apply to me, however, since 1) I’m right-handed, so the smaller one is my dominant arm and 2) 95% of my exercises are with dumbbells and resistance bands (doing one arm at a time), so obviously there isn’t any overcompensating.

10 years ago I had spinal fusion surgery and the surgery lasted much longer than anticipated. Since my arms were up above my head for a very long time, I started having issues with my right arm where it would go to sleep quickly and was very uncomfortable. At first it happened all of the time, but now it just bothers me at night. Back then the doctor checked to see if there was any nerve issues, but there wasn’t. I always believed it was a circulation issue and not nerve, but I never found out why this happens. Now I have this problem, so I made an appointment to get it checked out. Due to the Holidays, I can’t see my doctor for another few weeks, so I thought I would see if anyone else has heard of anything like this before and what are some things that I can do to fix this problem. If my circulation is poor in my right arm, wouldn’t that affect muscle growth? Thanks in advance for any feedback.

My dominant side, arm, shoulder, and leg, are all smaller than my “weak” side. The only conclusion I’ve been able to come up with is I use my dominant side for work and stuff, so my body has become very efficient at making those things work well.

My theory is that it’s easier to isolate and target certain muscles on my weak side, because my body hasn’t spent 28 years learning how to make that side stronger and more efficient. IE recruit more muscles around those areas to help in making it easier/more efficient.

It makes sense in my head.

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Without diagnosing you, you might wanna get checked for thoracic outlet syndrome

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