Dumbbells and Motor Unit Recruitment

[Clay Simczyk]

In October I stopped doing the bench with a barbell and started using dumbbells, not because of an injury, I was just sick of the bench. I had poor progress and pretty much started hating the lift.

Nevertheless, I tested my 1RM at the end of 2014 hoping I hadn't lost too much. What I was surprised to find was not only did my bench improve, it improved at close to the same rate as it did training with just the barbell. In May my 1RM was 252.5 and it went all the way up to 257.5 after 2-1/2 months of barbell training. At the end of the year I hit 265 after two months of dumbbell work only.

One thing I noticed while using dumbbells was my improved ability to grind out reps. While going through my novice progression I had no ability at all to grind out reps on the bench. I would have instant failures. This improved slowly as my training went on, but it improved much more during the last two months of last year.

It could be just the increase in volume. I went from 5x5 with the barbell to 4x8 with dumbbells. The programing was basically doing however many reps I could do until I could get 4x8, then I added weight. I didn't think my bench would improve because the weight was so much less. The last volume workout on the barbell was 210x5x5. I went from that to 80lb dumbells. The last dumbbell workout before getting 265 on the bench was 90x4x8.

My thought is that since dumbbells require more effort to maintain a straight path it improves motor unit recruitment more than the barbell does. I know when it come down to it you either get enough stress to make an adaptation or you don’t. I just didn’t think I would since the weight I was lifting for volume went down so much. I'd appreciate any thoughts from those of you who have more experience and brains than I.

[Miro]

Well, maybe the bench improved because your squat, deadlift and press went up (i.e. you got stronger)?

[Clay Simczyk]

I doubt that the systemic effect would be that great, plus I was doing the bench, just not with a barbell. I've had many times where one lift would stall, but the others would still go up. If the systemic effect would always be across the board, I'd drop the bench forever knowing it would still be going up.

[Adam Skillin]

My thought is that since dumbbells require more effort to maintain a straight path it improves motor unit recruitment more than the barbell does. I know when it come down to it you either get enough stress to make an adaptation or you don’t. I just didn’t think I would since the weight I was lifting for volume went down so much. I'd appreciate any thoughts from those of you who have more experience and brains than I.

Are you saying you think the dumbbell bench press recruits more motor units within the pectoralis, triceps, and deltoids than the bench press, or that you think it includes other musculature that the bench press neglects?

[Clay Simczyk]

Are you saying you think the dumbbell bench press recruits more motor units within the pectoralis, triceps, and deltoids than the bench press, or that you think it includes other musculature that the bench press neglects?

That is the point I started scratching my head over this. I think it uses more motor units within the same muscle group, but I was having some trouble finding if that is possible. In Rip's books it sounds to me like this is something that does improve through strength training, but it's also something that doesn't have a great deal of ability to adapt.

[Cody]

The barbell bench press uses more weight than the dumbbell bench press. That means the barbell uses more motor units than the dumbbells, period.

[Adam Skillin]

My thought process is that if the prime movers are recruited maximally in the bench press as opposed to the dumbbell bench press, that it would have to include more motor units in those muscles. Since the weight being moved is heavier. But I may be missing something, and there may be something about the differences in the movements that allows more recruitment in one muscle group vs another compared to the other exercise.

[Clay Simczyk]

Did my bench go up just from the volume?

[Adam Skillin]

The barbell bench press uses more weight than the dumbbell bench press. That means the barbell uses more motor units than the dumbbells, period.

Well, typing on the keyboard uses more motor units than the barbell bench press, because the motor units required to operate the hands are very intricate and small, and operate lots of very, very tiny muscles, whereas those used to extend the elbows and shoulders and adduct the humeruseseseses are comparatively much larger. But I agree with your general premise, when comparing sufficiently similar exercises.

[Miro]

Did my bench go up just from the volume?

Did you alternate DB bench with the press or were you doing them every session?