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There seems to be a general consensus in the bodybuilding community that bone density can be increase by weight-bearing exercises and that bone thickness(girth) will not change in adulthood(after the growth plates close). However, I was able to find the following sources that states that bone size can increase through weight-bearing exercises:

-" Moderate training will help build your bones; however, the greater the loads you lift, the bigger your bones will become." (https://www.livestrong.com/article/486880-bodybuilding-bone-size/)

-"Regular resistance-training exercises do have the potential to increase bone width, according to the BBC." (https://healthyliving.azcentral.com/bones-bigger-working-out-1980.html)

-"Bone’s response to these forces varies along its length. Near the joints, bones get bigger and more dense, whereas bone shafts tend to get bigger and thicker with little change in bone density." (https://www.sciencealert.com/here-s-what-exercise-does-to-your-bones)

I understand that it's impossible to increase bone length after the growth plates close, but is it possible to increase bone thickness(girth)naturally through weight-bearing exercises?

  • Is there any particular reason for asking this question? – rrirower Dec 11 '17 at 17:07
  • well, cause I have thin bones and I want to know if I can still make them thicker. But my research yielded different results, hence this question – Frank Dec 11 '17 at 17:10
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    How is it that you determined you have thin bones? – rrirower Dec 11 '17 at 17:18
  • Generally speaking, lifting helps bone density. The articles seem to point out that it is possible for the bones to gain some width as well. – ChasingTimmy Dec 12 '17 at 16:00
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Yes. Let's consider adulthood to be 18 years old. Notice the hip range of motion in basketball players as they age:

basketball internal range of motion

Source.

What we're seeing here is players lose internal rotation range of motion at the hip much more than controls. At least into early adulthood / ~early 20s. (Granted, early twenties, much less 18 years old, does not guarantee complete growth plate closure, but off the top of my head this is the best way to look at this topic.)

The reason for this is they're acquiring more bone at the top-front of the hip. The bone is thickening, in the yellow quadrant:

          basketball hip bone

That's because this area is getting loaded during running and jumping / landing. The pelvis and the top of the femur bang on one another with the hip a bit flexed. That is, that quadrant rotates some when we say, land with our legs somewhat bent:

         hip flexion cam impingement

Because the femoral neck gets bigger, it doesn't have as much room to bend or twist before it hits the acetabulum:

          femoral neck

         acetabulum

Animation of internal hip rotation:

         cam impingement

Note "Cam." This is a type of impingement at the hip.

hip impingement

Source.

This is the idea behind surgeries such as

  • Shoulder impingement
  • Hip impingement
  • Heel spurs

In the above, you tend to have some bony overgrowth, making it more likely two bones pinch -"impinge"- the structures between them. Thought process being shave the bone down, lessen the odds of impingement.

Precisely differentiating between genetic overgrowth or acquired has not been adequately done yet, and is not easy to do.

       -Longterm studies are hard

       -Hip impingement surgeries have been on the rise.

        -Are we better at diagnosis

        -found another way to make money

        -are more hips genuinely deformed from activity modification e.g. more kids playing sports?

        -is it because adults are loading their hips in flexion more i.e. sitting more than ever?

Hard to parse out.

It's an area ripe for research, however, we'll likely find what we seem to always find with the nature vs nurture debate- both matter.

A caveat though is how much nature or nurture matters can vary with lifespan. What happens early in life can leave an impression tough to overcome.

Notice how after having a fibula harvested, the tibia can grow to be the size of the tibia + the original fibula. Right side of person was harvested:

fibula harvest bone growth tibia growth after fibula harvest

From: Tibia Adaptation after Fibula Harvesting: An in Vivo Quantitative Study.

I know the question was about adulthood and this study is on kids, but I want to bring it up because that change took 3.5 years. Yet kids' bones heal about twice as quickly as adults.

So, to make a noteworthy bone thickness change in adulthood and you're looking at what is likely to be a significant amount of time. Easily years. That's a lot of consistent weight training. (It's not a surprise many with impingement issues have been doing a certain activity for years.)

Even then, I doubt anybody knows an adult who e.g. had small wrists, then some years later could see the person's wrists were obviously bigger. I certainly haven't seen that with any of my clients. Where you start matters. Everybody can get faster or stronger, right? But you can't turn a donkey into a thoroughbred.

The only exception to this I know of are acute injuries. Even in adulthood, after say, dislocating a finger, you can get some serious bony growth. Right side has been dislocated while left has not:

finger dislocation

It's unlikely that kind of reaction can occur from exercise. At least on any desired timescale.

Finally, I always mention with this type of stuff, when you gain something, you lose something. While you might be enticed by thicker bones, many are looking for thinner. A powerlifter loves thick bones. Someone interesting in running does not. Often what one considers to be a structural defect can be repacked into a structural advantage. Those basketball players, as their hips thicken, yes, they have less mobility, but they're also less likely to break a hip

More details on the hip-

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