I am able to do, with heavier weights, concentration curl, hammer curl, and preacher curl with little difficulty, but when I do barbell curls I get exhausted or it's like there is no stamina in me. I think I involve my upper back and, due to lack of muscle and strength there, I feel tired. I heard that neurons are released when we get used to an exercise and we are able to perform it efficiently. What can you say on this matter?
Can running daily or a day in week increase my stamina? I am tall about 5 feet and inches.