Effect of the shoulder position on the biceps brachii EMG in different dumbbell curls

Incline dumbbell curl (idc) and dumbbell preacher curl(dpc) are two variations of the standard dumbbell biceps curl(dbc), generally applied to optimize biceps brachii contributionfor elbow flexion by fixing shoulder at a specific angle. the aimof this study is to identify changes in the neuromuscular activityof biceps brachii long head for idc, dpc and dbc exercises,by taking into account the changes in load moment arm andmuscle length elicited by each dumbbell curl protocol. a singlecycle (concentric-eccentric) of dbc, idc and dpc, was appliedto 22 subjects using a submaximal load of 40% estimatedfrom an isometric mvc test. the neuromuscular activity ofbiceps brachii long head was compared by further partitioningeach contraction into three phases, according to individualelbow joint range of motion. although all protocols elicited aconsiderable level of activation of the biceps brachii muscle (atleast 50% of maximum rms), the contribution of this musclefor elbow flexion/extension varied among exercises. the submaximalelbow flexion (concentric) elicited neuro muscularactivity up to 95% of the maximum rms value during the finalphase of idc and dbc and 80% for dpc at the beginning of themovement. all exercises showed significant less muscle activityfor the elbow extension (eccentric). the incline dumbbell curland the classical dumbbell biceps curl resulted in similar patternsof biceps brachii activation for the whole range of motion,whereas dumbbell preacher curl elicited high muscle activationonly for a short range of elbow joint angle.