The other day I got a question from someone asking if single-arm upper body exercises are more beneficial as opposed to two-arm upper body exercises. This was a great question and I really wanted to jump into the subject and show off, but it would have been a rather long winded answer, so I gave a pretty simple and concise answer to save the guy listening to me yammer for 20 minutes plus. Instead I'm going to throw it all out on here.
There are a couple levels of how one sided you can really get when it comes to upper body exercises. Let's get clear on this right now, two-arm exercises, mostly consisting of exercises involving a barbell or bar, are NOT bad for you. They allow easy movement for those that are not so advanced or experienced with lifts. A bar will also keep the shoulder from going too big of a range of motion if there is an injury to the shoulder and you are trying to avoid certain shoulder movement patterns but still want to get some work in. The shoulder doesn't magically stay out of that movement pattern remember, you have to perform the exercise correctly still.
Performing all the same exercises, and a few others your really can't, as you do with a bar with 2 dumbbells can be and is more beneficial. Reason I believe so is because with dumbbells in hand you have a better range of motion in your shoulder because the bar limits you from moving your hands in and out (abducting and adducting your shoulder). Before we get to far, ladies, and some gents, please for my sanity and any other good fitness professional's out there, please put down the pink dumbbells. Results will come without your precious pink beauties, I promise. The number of actual exercises goes higher when using dumbbells because of the freedom of movement (lets see you do a lateral raise with both hands on a single barbell). The ability to switch up your routine with more exercises means that your brain won't get bored so easily and you can stick to your program.
Last little nugget I'm going to throw you for this one. We all have a dominant side that we are stronger on and more confident using. These eventually, if it hasn't already, will develop deficiencies in your movement patterns and even your posture. Concentrating on using one side at a time can actually allow you to correct some of these issues. More than that once you get use to doing so you will be able to lift more per side than if you used both at the same time. The simple reason to answer why this happens is because your put more concentration into the one side than when you use both sides and put in as much effort. Using dumbbells in either case will also help you with those stabilizer muscles simply because the bar isn't there to help you hold everything steady.
That's it for today everyone, hope this helped someone out there today.