In case you rest your arms about the preacher curl bench, you minimise the involvement of other muscle teams, which include the deltoids or upper back. This permits for a more targeted and rigorous contraction with the biceps. A barbell curl is a pull-variety isolation physical exercise that actually works primarily on your biceps https://www.theorthopaedicandpainpractice.com/understanding-burning-pain-in-the-upper-right-arm-causes-symptoms-and-treatment-options/