🚨 BARBELL SHRUGS
✅ To strengthen the upper trapezius muscle, shrug against resistance is usually performed. However, some authors have proposed that a variant of this exercise with a shoulder abduction of 30 degrees would allow better muscle activation, but no study have yet investigated this point.
🚨 A Team of Australian researchers compared muscle activation in two shrug variants. Researchers recruited healthy subjects (11 women and 12 men) and patients with multidirectional glenohumeral instability (MDI) (7 women and 7 men). All participants made two dumbbell shrug variants :
- ✅ A standard shrug : the arms along the body (right drawing)
- ✅ A modified shrug : with shoulder abduction of 30° (left drawing)
💡 For each variant, all the participants performed 10 repetitions under both conditions. The concentric phase and the eccentric phase took each 2 seconds to complete, and 30 seconds of rest was allowed between each repetition, to avoid the effect of fatigue. The load corresponded to about 25% of the isometric maximal voluntary contraction (CMVI) when the shoulders are at 90° of abduction. Thus, the group “Healthy” used dumbbells of 2.5 kg and the group “MDI” dumbbells of 2kg.
✅ Under both conditions and at each repetition, the electromyographic activity of the upper, middle, lower trapezius and serratus anterior muscles was recorded. Moreover, to put the observed results in perspective, the maximum voluntary isometric contraction (MVIC) was measured for each muscle in 4 different positions.
✅ The main results of this study show that the shrug variant with arm abduction of approximately 30 degrees allows significantly higher muscle activation of the upper and lower trapezius in all participants. This because the arms abduction allows a better trapezius muscle activation, including the upper part, maybe due to the change in the contraction axis of the fibers compared to the classic version of the shrug, with arms along the body. The external scapular rotation caused by the abduction of the shoulder facilitates this.