main agonists

M. trapezius, Pars descendens
M. deltoideus, Pars acromialis
M. supraspinatus

synergists

M. trapezius, Pars transversa
Mm. rhomboidei

Description:

You need the straps. Your legs are spread so that your feet are under your hips. You are leaning slightly forward with a straight back. Your elbows are pointing upwards. Your hands are at the height of your clavicle. Pull with maximal force for about 5 seconds.