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

Abstract

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 (STflex) or not flexing the arms (STno-flex) or the EZ barbell flexing (EZflex) or not flexing the arms (EZno-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 STno-flex vs. EZno-flex (+1.8%, effect size [ES]: 0.74), in STflex vs. STno-flex (+17.7%, ES: 3.93) and in EZflex vs. EZno-flex (+20.3%, ES: 5.87). During the descending phase, a greater nRMS was observed in STflex vs. EZflex (+3.8%, ES: 1.15), in STno-flex vs. STflex (+2.8%, ES: 0.86) and in EZno-flex vs. EZflex (+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.

Biceps Brachii and Brachioradialis Excitation in Biceps Curl Exercise: Different Handgrips, Different Synergy

“…The present investigation was designed as a cross-over, repeated-measures, within-subject study and was conducted in line with previous studies from our laboratory [ 13 , 24 , 25 , 26 , 27 , 28 ]. The participants were involved in five different sessions ( Figure 1 ).…”

“…We recruited 10 male competitive bodybuilders (age 29.8 ± 3.0 years; body mass 77.9 ± 1.0 kg; stature 1.68 ± 0.01 m; training seniority 10.6 ± 1.8 years) for the present procedures, in line with previous studies [ 13 , 24 , 25 , 27 , 28 ]. They had to be clinically healthy, without any reported history of upper-limb and lower-back muscle injury and neurological or cardiovascular disease in the previous 12 months.…”

“…The area of the appropriate electrode placements was first checked by means of a 13 × 5 semi-disposable high-density electrodes matrix for sEMG detection (GR08MM1305 model, inter-electrode distance of 8 mm, OtBiolettronica, Turin, Italy), as carried out in similar previous studies [ 13 , 26 ]. The sEMG signal was acquired by a multichannel amplifier (EMG-USB model, OtBioelettronica, Turin, Italy; input impedance of >90 MΩ; CMRR of >96 dB; EMG bandwidth of 15–350; gain × 1000).…”

“…However, the use of different tools during the execution of the exercises and the handgrip changes during the execution of the dumbbell biceps curl introduced two variables hindering the effect of the grip per se on the excitability of biceps brachii and brachioradialis. Comparing straight vs. EZ barbell, the straight induced slightly greater excitation of the biceps brachii, while no information was reported about the brachioradialis [ 13 ]. Conversely, no difference in biceps brachii and brachioradial excitation was found while performing dumbbell biceps curl with a supinated and neutral handgrip at different inter-hand distances [ 14 ].…”

“…Examining the ascending and descending phase individually, the importance of independently investigating the two phases comes from the distinct acute neuromuscular characteristics [ 15 , 16 , 17 ], the recovery time course when focusing on the descending phase [ 18 , 19 , 20 ], and the long-term neuromuscular and structural changes [ 21 , 22 ]. For example, the abovementioned study split the analysis into ascending and descending phases and reported definite distinctions between the exercises [ 10 , 13 ]. In addition, bodybuilders show the ability to perform a given exercise with a consistent technique, increasing the trustfulness of the outcomes [ 23 ].…”