So after a decent break from weightlifting, I started again about three months ago. 48 male with an office job decently athletic

I do a standard push pull legs with a fourth day of full body workout plus some CrossFit exercises and one or two days of about an hour of cardio

I noticed today that my left bicep which is my non-dominant hand and is weaker than my right arm is more defined than my right bicep

Any thoughts how I can work on getting my right bicep more defined over the next couple of months or just stay the course?

While I do use the cables and barbells, I do favor the dumbbells for the majority of my exercise exercises for my upper body