Adjustable Dumbells and Their Benefits
Adjustable dumbells are great. They have many advantages over bar and plate weights and weight machines, and can really fit well into a small area of your home or gym. On top of their size advantage, they do a much better job isolating all your peripheral and supporting muscles during an exercise than solid-bar lifting does, and a much better job than weight machines in general. The reason for this is pretty simple, but let’s start with the shortcomings of solid-bars and machines
Looking at weight machines, you’re basically lifting a weight attached to a hinge. That means that the arm the hinge is attached to can only follow a set arc, and will not take any effort to keep from deviating left or right, front or back. All you have to do is push the weigh up and down, and this movement only strengthens very specific muscle groups, depending on which exercise you’re doing. Not so with adjustable dumbells.
If we take a look at solid-bar weights, we’re eliminating one of the supports, but the other still exists in some form or another. That is, free weights can fall forward or backward if you don’t stabilize them where on a machine they cannot. Too, they require some effort to keep from falling side to side, but not as much since the bar is linked and your arms are working together in the effort to stabilize. So the conclusion is that solid-bar free weights are better than machines, which are better than nothing.
Now let’s analyze adjustable dumbells. You have two independent weights that your arms must not only push up, but also keep from falling out, in, back, forth, and every other direction. And they must do this with no stabilization from the other side. So, with a solid-bar setup if the bar is moving to the left with a 2 Nm force, each arm really only has to contribute half of that to stabilize it. With a separate weight in each hand, the arm with the weight in motion will have to correct the movement by itself. This makes both arms stronger.