T Nation

One Arm or Two?


My brother and I have an ongoing debate about training pecs and lats. I say, that in order to train these particular muscle groups properly, one has to stress both sides at the same time (i.e. have a dumbell in each hand even if you are contracting one side at a time). My reason for saying this is that I thought the pecs and lats contract against each other to perform a task. He takes the opposing view. He believes that you can train these muscle groups effectively totally isolating one side at a time.

What do you think?

If anyone could tell me where i might be able to find some research or literature on this question that would help as well. Thanks..


Hi E-Dub,

Not so. Try doing 1 arm chin-ups sometime. Even without weight in the other hand you will be working the lats hard (very hard). The same could be said of 1 arm push-ups.

By the way, what caused you to be under the impression that both sides had to be stimulated at the same time? And, what led you to believe that the Pecs and Lats were any different than any other muscles?

One more thing, actually from a biomechanical standpoint, the pecs and lats are not opposing muscle groups. The lats oppose the deltoids, while the pecs oppose the traps.

Good training,



Thanks Sento,
I'm glad that someone finally gave me a response. The reason I have gotten this notion in my head- I read an article in a prominent muscle mag a while back reguarding this training theory. I don't think I explained this very well though.

What I mean by opposing is that the left pec contracts at the same time as the left (and vice versa) in order to create maximum push.  I think the jist of the article is that in order to train the pecs and lats "optimally" you must be stressing both sides.

 I don't know if that makes it any clearer.  Or maybe the article was a bunch of crap.


Well, muscles cannot actually push anything. Muscles pull on limbs/body parts. So, other than neurologically, there would be no reason for a stronger contraction during bilateral vs unilateral movements.



Hmm, Thats a good question... No doubt you would work your lats pretty hard doing a one arm pullup because that one side has to handle so much weight, but would each side repspectively be able to handle more weight if you did heavy weighted chins?

Thats a hard one. I would argue that since the angle has changed with a one arm pullup the actual degrees from the spine to the insertion on the humerus would be greater in a two arm pullup due to the fact that the spine is stabilized by the other arm hanging on the bar and you could potentially get a better stretch of that muscle...


Pecs and lats can be opposing muscle groups, for instance lats are the prime movers in a 1 arm dumbell row, and pecs prime movers for a bench press. In these movements the oppose each other. However, since the shoulder is such a mobilized joint there are not as many black and whites in regard to antagonistic muscle groups go. The rear deltoid also assists in many lat dominant movements as well, so the shoulder and lats are not opposing muscle groups.

The lat vs. the pec is right on though. Try doing a straight arm pull down with your side facing the cable. You will likely be able to hit the pecs and lats, because in that motion those muscle are both adducting the arm.


I think this might be what the article was trying to get at. I don't think it was saying that there were no benefits to total isolation of one pec or lat. It was trying to say that optimal results were achieved by stressing both sides at once. I think what your saying about spine alignment and greater stretch might be the answer as to why.


Hi shadowzz4,

Well, that really depends on how wide a grip one takes during the two arm pull-up. Also, with the one arm chin-up (OAC)there is a much greater range of motion as compared to a two arm pull-up (both in the stretch at the bottom of the exercise, and the degree to which the upper arm can be pulled into the side of the body). In my experience using as great a range of motion as possible is key to developing strength and/or hypertrophy.

Which brings up a good point. What was the focus of the article? Since E-Dub said he found it in a muscle mag, chances are they were focusing on hypertrophy. But, then again, most muscle mags will still tell you that wide grip pull-ups are the best exercise to build wide lats.

As far as whether or not each side could potentially handle more weight doing heavy weighted chins vs. OAC's, I seriously doubt it. Also, it's the amount of force that the muscles in the movement must produce that matters, not necessarily just how much weight they must overcome. First realize that in order to even duplicate the amount of weight being placed on the muscles during a OAC you would need to do a pull-up with your bodyweight added (which few people can do), then take into account that the OAC requires considerably greater amounts of coordination and stabilization than a two arm pull-up. And, if you did develop the ability to add more than your bodyweight to a two arm pull-up, you would probably still get greater results from adding weight to the OAC.

Take a look at rock climbers some time. They have proportionally huge lats, and many of them routinely do OAC's (many while holding a barbell plate in the free hand).

Finally as to whether the pecs and lats are opposing muscle groups. First, let me state that I was referring to the muscle being the prime movers in the movements. Yes, the rear delt does assist in horizontal shoulder adduction and in shoulder adduction. But, it is not the prime mover in either of these movements.

During a 1 arm dumbell row where the elbow is kept close to the side of the body, thus making the movement of the humerus primarily a shoulder extention movement the lats are the prime mover. However, if one were to reverse the movement at the humerus the action would be shoulder flexion (in which the prime mover is the deltoid muscle, primarily front head). This is not the movement utilized during a bench press. The movement utilized during a bench press would be horizontal shoulder abduction (where the humerus is out away from the side of the body) wherein the pecs are the prime mover. The opposite of this motion would be a row where the elbow stays away from the side of the body (anywhere from perpendicular to the body's vertical axis to about 45% from it). The prime mover in this action is the traps which therefore oppose the pecs. The further away from the body the more of a pecs/traps emphasis there is, the closer the more of a deltoid/lat movement it is.

Good training,