Bilateral Biceps Curl Shows Distinct Biceps Brachii and Anterior Deltoid Excitation Comparing Straight vs. EZ Barbell Coupled with Arms Flexion/No-Flexion

The present study investigated the excitation of the biceps brachii and anterior deltoid during bilateral biceps curl performed using the straight vs. EZ barbell and with or without flexing the arms. Ten competitive bodybuilders performed bilateral biceps curl in non-exhaustive 6-rep sets using 8-RM in four variations: using the straight barbell flexing (ST(flex)) or not flexing the arms (ST(no-flex)) or the EZ barbell flexing (EZ(flex)) or not flexing the arms (EZ(no-flex)). The ascending and descending phases were separately analyzed using the normalized root mean square (nRMS) collected using surface electro-myography. For the biceps brachii, during the ascending phase, a greater nRMS was observed in ST(no-flex) vs. EZ(no-flex) (+1.8%, effect size [ES]: 0.74), in ST(flex) vs. ST(no-flex) (+17.7%, ES: 3.93) and in EZ(flex) vs. EZ(no-flex) (+20.3%, ES: 5.87). During the descending phase, a greater nRMS was observed in ST(flex) vs. EZ(flex) (+3.8%, ES: 1.15), in ST(no-flex) vs. ST(flex) (+2.8%, ES: 0.86) and in EZ(no-flex) vs. EZ(flex) (+8.1%, ES: 1.81). The anterior deltoid showed distinct excitation based on the arm flexion/no-flexion. A slight advantage in biceps brachii excitation appears when using the straight vs. EZ barbell. Flexing or not flexing the arms seems to uniquely excite the biceps brachii and anterior deltoid. Practitioners should consider including different bilateral biceps barbell curls in their routine to vary the neural and mechanical stimuli.