Physics: rotating dumbbell vs. fixed dumbbell

To address the question of whether muscle isolation is a good or bad thing, Mark Rippetoe unmistakably advocates working as many muscles as possible in conjunction with each other.

In an excerpt from his book Starting Strength, Rippetoe says:

ETA: If you’re looking for this quote, it’s in the last paragraph on page 8.

No one is questioning that.

I would agree with this. Not having a firm grip is just asking to get injured. The problem he is encountering is that with fixed dumbbells, he cannot have both a firm grip and avoid the rotation, with sleeves, he can.

And there is potential benefit, depending on what the focus of the exercise is. The rotation definitely puts excessive stress on the wrists, particularly with large amounts of load on the tendons and ligaments, where the intended focus of a snatch is on the larger muscles.

I’m firmly in the school of avoiding assistance whenever possible, like not using wrist straps, wraps, or belts, but it all depends upon what your goals are. As I’m training for overall strength, fitness, and all that, I generally get better results that way. If, however, I were body building, power lifting, or doing some other sort of activity specific training, there are safer and better ways to train the support muscles without that added stress from a high impact exercise like snatches.

That said, I broke my wrist in high school, and it took a long time to recover, but I also LOVED to do snatches. I can definitely say that the rotation put a lot of stress on my, then, weak wrists, so I can understand why someone would want to eliminate that aspect of it.

The stress of stopping the momentum of a heavy dumbbell at the top of the movement (which you’ll get with either dumbbell) is going to put more stress on your wrists than the 180° spin a fixed dumbbell has from start to finish.

It will be greater total force, but I cannot agree that that makes it meaningfully greater stress because the type of loads, and the muscles/tendonds loaded are different. The rotational stress will include load onthe extension muscles and tendons, whereas the stress of stopping the momentum should be primarily on grip strength, with those others serving only as stablizers.

From my own experience when dealing with rehabing my wrist, I found the rotational portion irritated my wrist noticably more than stopping the momentum at the top of the movement. Now, of course, I never did it with free-spinning weights, so I cannot say for certain exactly how much it may or may not help, and whether or not it makes it worth it. And though I maintain that you cannot directly compare those stresses, the point still remains that is still removes one, and that if one is also concerned about other stresses on the wrist from the movement, then one could also use straps and wraps.

My problem is pushing the use of the smith machine, and isolation exercises for general people. I really don;t have the time to google all kinds of cites about the dangers of smith machines, but here is one I already had:

And here is a short list of problems with the smith machine from a person called Ivey on the Mens Health forum (Yes, he is not any kind of authority on the subject, but he is saying what I am thinking, so I will quote his words)

"1. Pattern Overload Syndrome: The Smith machine locks you into a fixed plane of motion, which can lead to what is known as ‘pattern overload syndrome’. The more fixed the object, the more likely you are to develop a pattern overload, and the Smith follows an extremely fixed pathway. This fixed pathway repetitively loads the same muscles, tendons, ligaments and joints in the same pattern, encouraging micro-trauma that eventually leads to injury. If you always uses a Smith machine for your bench presses, you end up working the same fibers of the prime movers in the bench press all of the time: triceps brachii, pectoralis major, long-head of the biceps brachii, anterior deltoids, and serratus anterior. You can’t change the pathway; the bar will always be in the same position. This commonly leads to chronic injury over time.

  1. Reduced Stabilizer Training: The weight is stabilized for you. However, joints normally operate in multiple planes, and recruit a myriad of other muscles to help stabilize load. Use of the Smith machine greatly decreases this stabilizer activity. This creates a problem when translating your strength and muscle gains back to real life. If you have not trained the stabilizing muscles, you create size and strength imbalances in these muscles that would normally be assisting in the lift. In addition, having weak stabilizers will serve to shut down the prime movers before the prime movers are ready to shut down. If the stabilizers cannot maintain joint integrity there is a feedback mechanism that will cause the prime movers to shut down, or “fail.” When you’re helping your buddy lift that heavy piece of furniture, or pulling that heavy sack of groceries from the back seat of your car, it won’t be attached to a bar that assists your move and travels in a straight up and down plane of motion.

  2. Compromised Center of Gravity: When you squat with your knees out in front there is added pressure on the spine. When you free bar squat, the path of the bar is traveling over the instep of your foot and you are driving through your natural center of gravity (COG), the COG you create by moving your hips back and bending your knees on the decent of the squat. When you are on a smith machine with your feet positioned out in front, you are causing your body to drive through a false center of gravity. Now, instead of the weight being over your feet, it is directly in-line with your spine and your feet are out front, placing your new (false) COG somewhere about mid thigh. The problem this poses is that your spine is not in a healthy position to stabilize force. Your hips are there not only to move the lower body, but also, to stabilize forces being placed on the body. If you put them out front you take that ability away from them causing all of the weight to be compressed on the spine without anything to absorb the shock. NOT GOOD!

These principles clearly apply to any exercise you might want to do on the Smith. Take, for example, the squat. Because of the mechanics of the knee joint, the body will alter the natural bar pathway during a free-weight squat to accommodate efficient movement at the knee. A fixed bar pathway doesn’t allow alteration of the plane of motion for efficient movement of the joint, thereby predisposing the knee to harmful overload via lack of accommodation. And, for all of you that like to put your feet out in front of you, in addition to the COG problems outlined above, if your feet are out in front of you, you tend to push back against the bar. Doing so changes the function of the hamstrings role in the move, removing it’s stabilizing, protective effects on the knee joint. The result is an increased sheering force on the knee. Again, over time, chronic injury, and even possible traumatic knee injury."
I believe the smith machine is a horrible tool, and I don’t want to see people hurting them selves based on information they read online.

It may have its place for lifters who already have experience when used as a supplementary exercise. But I feel that telling inexperienced lifters to use the smith machine for their main lifts is like telling a 16 year old the best way to learn how to box is to get in the ring with Evander Holyfield for three rounds. It probably won’t end good.

You missed my point. The reason he doesn’t like using fixed dumbbells for doing exercises like the snatch is because you have to use a loose grip and let it spin. That’s why he has the dumbbells with the sleeves and the slop, so that you can have a firm grip and still have the weight rotate. Notice that the fixed dumbbells go up to what appears to be about 30 lbs. each. After that, the heavy dumbbells are all sleeved versions. I’m sure that’s not a coincidence.

Actually, the smith machine has been perfected by Hoist.

It ain’t cheap but it’s good.

What’s the point of using that instead of a free weight?

^ Can you guys take the Smith machine argument to another thread, especially since it now involves claims copied and pasted from an anonymous poster in another thread? Thanks.

Stopping the momentum of the dumbbell is not be a matter of grip strength; it’s a matter of stopping the wrist from hyper extending and using the delts to stop the momentum. The dumbbell rotating 180° from start to finish will be negligible by comparison.

How can you claim I missed your point when I directly responded to it? You do not have to use a loose grip and let it spin. That’s a ridiculous statement. Plenty of people are doing them with a firm grip and no rotating sleeve. No one is doing them with a loose grip. Here are some videos where folks are not doing what you say needs to be done:

Yes, that’s what this thread is about. :confused:

The first two are light weights, which wouldn’t really matter much, and on the last one it looks to me like he is indeed doing exactly what I said; letting his hand shift around the grip of the weight at the changeover point. He’s very obviously not rotating the whole weight. Believe me, you’d see it if he were rotating 75 lbs. with a tight grip on the weight.

You already know what I think and what Rippetoe thinks. I’ve done that exercise enough to know how it feels with different weights. I’ve made up my own mind from experience. Get some of your own and figure out what you think. I’m not particularly interested in debating stuff that’s pretty damn clear-cut when you do it and see for yourself. You don’t agree? That’s fine. Your disagreement isn’t going to dump a heavy weight on my head, so you can think whatever you want to.

But don’t take my word for it. Tell you what, go do some heavy dumbbell snatches with both fixed and sleeved dumbbells and tell me which one you think is better for the movement. Make up your own mind.

The weight used in the first video is 40lbs. The one in the last video doesn’t look much if any heavier than that. Regardless, the requirement you repeated twice does not exist.

How did you conclude that in the last video that it looks like the man is loosening his grip and allowing his hand to spin around the bar? I see no indication of that and I watched the video frame by frame.

Oh really?

When using fixed sleeves instead of free/sleeved ones, and you use the same weight:

fixed = greater stress/force on the gripping skin/contact area and wrists and other stabilizers

sleeved = less stress/force on the gripping skin/contact area and wrists and other stabilizers
If you can do more weight, more safely with sleeved barbells, isn’t that because – like other machines that isolate – you are backing off the stress introduced to other secondaries (skin, wrists, etc).?


Watch the second half of the video, where you see the side view. You can see the clips on the ends, and they’re clearly rotating. Yes, you would see it if he were rotating 75 pounds. And you do.

My gym has just changed its dumbbells from spinners to non-spinners. I can confirm that the non-spinners put a LOT more stress on the wrists BUT only in certain exercises. Personally, I think anything that stresses my wrist with rotational force is to be avoided.