This is the same for Smith machine upright rows, whether done with two arms at a time or one. The sense is because doing them with a wider grip allows the elbows to lift out to the sides in a similar procedure to lateral raises. Save the difference is that therefore you are pulling the weight up, you can custom more weight to place more overload on the middle deltoid head for greater muscle growth. And although you all have felt and seen the reward from doing upright rows this way, I’ll still notice a unaccustomed study that supports this pattern of upright rows.
Researchers from the University from Memphis, yes in Tennessee, had trained subjects perform the stile row with a close grip (half of shoulder width), a shoulder-width grip, and a two times wider than shoulder-width constrict on the bar.
They measured muscle activity of the front, middle and rear deltoids, as well being the upper and middle traps, and biceps during upright rows.
They reported in a 2013 issue of the Gazette of Strength and Conditioning Research that when the subjects performed the ethical row using the two times shoulder-width grip, the power activity of both the mid deltoid and even the rear deltoid increased by over 20% compared to using the faithful grip.
They also reported that the wider grip increased muscle activity of the upper traps, whereas decreasing muscle activity of the biceps.
Jim’s take-home point:
As you should already be doing, this study confirms that doing the upright row, whether with a standard barbell or in a Smith machine, with a wider than shoulder-width grip increases muscle activity of the middle deltoids. It yet increases muscle activity of the traps, which is somewhat surprising. But also surprising is the fait accompli that the wide-grip upright row also increased muscle activity from the rear (posterior) deltoid head. So use the upright row in this manner for ameliorate development of both the middle and rear delts, as well as the traps.