Why I think the neck weight solution is wrong

[gravatar size=18 align=absmiddle email=sanne.buurma@gmail.com] This is a post by [the_author_posts_link].

This is the first article in a series about finding a better design for the weight needed in a dynamic pool freediving performance. This article focusses on my discomforts and dislikings about the current design, which I blindly followed when I first started freediving. The next article in the series will focus on the way I intend to solve these problems into a new solution and the design around it. In the 3rd article I will focus on the testing we’ve done so far with different setups, to see if they actually solve my problems. The 4th article will show how the design evolved through time by incorporating our findings in the test phases. Finally in the 5th article I hope to present a solution with an easy design, so other freedivers can try and build one of their own and see if they benefit from it as much as I do.

The prototype I had recently tested, started out with an idea to get rid of my discomfort in wearing a weight belt around my neck. There are a few reasons why I dislike the neck-weight solution;

  1. Weight placement
  2. Unbalanced alignment
  3. Blocking optimal arm position

Weight placement
Why I think the weight placement at the neck is wrong, comes from the lung placement in a human body. The center of mass for a human being is located in the lower abdominal regoin, where as the center of buoyancy of the body immersed in water is located in the middle of the lung area. Which is a substantial distance apart when placed horizontally, besides the fact that it differs a between different body types. If you want to compensate this and bring balance to the scale, next thing you want to think about is weight placement.

When a person of average build tries to float horizontally on the back with arms along the sides of the body, the center of mass is nearly level with the center of buoyancy. Many people have more body weight in their legs and hips because of the high proportion of muscle tissue there, so their center of mass is near the hips. Thus when trying to float in a horizontal position, gravity pulls the hips and legs downward while the buoyant force of the water pushes the chest area (center of buoyancy) upward. The body rotates until the center of mass is directly below the center of buoyancy, resulting in a diagonal body position. At that point, the person should float motionless.

A human bodies’ center of buoyancy is a point around which the buoyancy forces are balanced. My problem with the neckweight is that my back-muscles are over compensating to keep a straight back. Compare it to holding a crate of beer out in front of you with straight arms or holding it close to the chest, you’ll find that holding it closer will require less effort to keep your back straight. Now imagine the same for the dynamic freediving position of the body with arms fully stretched; would you hold a weight for compensation in your hands? My point is not that the neck location is wrong, but focusses more with being able to last longer if the weight is located closer to the point around which the buoyancy forces are balanced.

Unbalanced alignment
The second reason for disliking the neck weight is the unbalance it introduces into the glide phase. It’s a fact that it is hard to ensure the lead to be equally distributed throughout the tube and requires proper craftsmanship. If it is not equally distributed, in the glide phase I find myself tilting left or right depending on which side has a little bit more weight. Even when the weight is distributed equally, I still find myself tilting, but this is caused by different strength in my arms or imprecise arm movement.

These phenomenons would pose no problem to the dive, if they were corrected by the weight. But the tilting during a glide phase is not corrected by the neck weight, because of the equally distributed lead. If I am to introduce a correcting & dampening factor for the neck weight, that would solve the problem of tilting, which is now neglected by the old designs.

Lately some improved neck weights, the one Daan calls the ‘Big Fat Bastard’ version 3, already solves a part of these problems, but introduces another discomforting factor; when you make a powerful arm stroke the weight is accelerated a tat slower than your body and lags behind your motion, than when it is accelerated it swings back giving your lower jaw a nice blow.

Blocking optimal arm position
The third problem I have with a neck weight is that in most cases the tube filled with lead will make it close to impossible to strive for optimal arm position. I myself don’t have a particular large gap between my arms when I place them in optimal position. Which is making it very hard for me to fully stretch my arms out without choking myself with the neck weight.

Although this sounds a minor detail, swimming with comfort is an important factor, the BFB 3 solves the problems with the old design by keeping the parts around the neck very thin. But a thin wire like solution, introduces a smaller surface area which has to distribute the weight on to your neck.

My 2 cents
These are just my dislikings with the current and old designs, there’s nothing wrong with them as people are swimming extremely far with them. I just hope to set sail on a journey to improve the sport of freediving by sharing my ideas. I am not the only one out here trying to improve this, so let yourself be heard and post your ideas in the comments.

I’ll share my thoughts on how I think I’m able to solve my problems & dislikes with the neck weight in the next article in this series.

12 thoughts on “Why I think the neck weight solution is wrong”

  1. hey sanne this is pretty interesting. I also dislike neck weights, from limited experience, because of the feeling of restriction around the arms. I haven’t noticed the tilting effect, but how would a weight, neck weight or otherwise, produce a dampening effect? Wide or narrow distribution of the weight? Your remarks about the the body’s centre of mass makes me think that the lungs work like fulcrum on a lever; and in this sense the neck is further away than the shoulders, requiring less weight to correct the body than a weight on the shoulders or back, but more than a weight than on the head or arms – assuming the body remains as stiff as a lever which of course it doesn’t and can’t and thus lies the problem. I remember reading about someone who made an ergonomic but non-flexible weight moulded to the back of the neck, but the disadvantage was it prevented the diver from looking up…! Anyway, to solve the problem I suggest a shoulder weight comprised of a pattern of small spheres of element 118, or perhaps lead 🙂 , ‘sewn’ into a flexible, stretchy, but non-buoyant garment worn around the neck, head and shoulders.

  2. I’ve been seeing the same problem: my legs drag and I lose glide.

    I haven’t tried it yet, but my thought is to use wetsuit pants to provide some bouyancy for my legs, and weights across my back. My plan is a bicycle inner tube in a figure-8, with 4 to 5 kg across my back. haven’t tried it yet.

  3. Do not forget the safety aspect of being able to take off a neckweight quickly (by the safety crew in case of a blackout or in very good trained divers by them salves before a problem happens) .
    Most solutions with harnases disqualify for this reason.

    The leg dragging is easily solved with a thin pants. I have been doiing this for years since my legs are very negative. Then a neckweight and a thin trimming weight around the waist to balance the slightly overbuoant pants.
    The discomfort issue still stands unfortunately. Too loose and dangling , too tight and discomfort. It is a difficult balance and i am already on my 10th neckweight i think. This is getting very close to how i want it.

  4. p.s. Rolling of the body should not be solved with lead but with better technique in my opinion.
    Same reason why you do not fix bad mono technique with an odly shaped mono to overcompensate an error you have 😉

  5. There is another reason why you can roll a bit that is not lead or technique related. Jet squirts from the side of the pool. There are 2 in my pool and every time i pass one i tilt 20+ degrees.
    The better you are perfectly neutral the more you feel the effect. Like a ball perfectly balanced on the top of the hill only needs a slight tick to roll over.

  6. @Glenn Venghaus Thanks for all the input, these are all valuable comments and I’ve taken them under consideration if I not already had them in my basis of design criteria.

    I understand your point of view on the rolling part and agree that I’d like my technique to be that good as well to not roll during my performance, which should be priority one by putting in a lot of training effort. But wouldn’t it be an added value that; when you’re getting close to your maximum and technique seems to fail here and there or the jet streams in a pool make you tip, that the placement of the weight – you already had to carry anyway – helps you in balancing out while gliding?

    It’s just that I’m trying to optimize the placement and whilst doing so create some added value along the way.

    Thanks again for your great feedback.

  7. Hi Sanne,

    Your post is about a month old now but just now did I notice the comments…

    At the end of long dynamics I start to sink ever so slightly since I am neutral in the water at the beginning of my dives (where I am most relaxed and have longer glide phases). I did no really test this but I am pretty sure that my balance shifts a little during the dive.

    Just an observation – not sure what to do with it.

  8. Hi Sanne,
    I'm an amateur free diver, swimmer and scuba diver, so I won't have anything of my own personal training experience to offer. However, the reason I ended up on your blog (congrats on your achievements btw) is because I'm writing a fiction book and am adapting my human characters to underwater life. While I was reading your blog and learning about monofins and neck weights etc, and read your analysis of buoyancy/centre of mass location, it struck me that you might want to consider looking at the anatomy of the marine animals you are emulating (I've been researching marine mammals as well 🙂 ), as the design and location of the weights might successfully copy those of a marine monofin. Just my two bubbles worth.

    1. Hello Forester, thanks for your feedback. I'll have a look for that theory you suggest, as it makes sense to also check that part out more thoroughly. Currently I'm on a good path on finding the optimal location and a surprisingly easy way to wear it. I'll post about that in a the coming weeks.

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