Hi. For a couple of last weeks I didn't grow a millimeter of muscles on my biceps. Today I made a video of my training and I did exercises without breaks between them. Then at the end of my training I found out that my arms were bigger which haven't happened during my last weeks of training when I had 1-2 minute breaks between each exercise. H-m-m-m. So, I guess I needn't have breaks unless it's really necessary? Yet it was really bad to not have a break between the first two exercises. Muscles ached a lot and I had to shrug my shoulders a bit (unconsciously) to keep doing the second exercise.