Bone Density and Lifting Weights

Hey. A friend of mine says building bone density by lifting weights is "rubbish". I know it does, but I dont know why. Can anyoen explain why lifting weights builds bone density? Thanks

The general principle is that as a muscle gets larger and/or
stronger, it is capable of exerting greater contractile forces.
The associated connective tissue and bone must also
increase in strength to be able to handle the increased forces
that the muscle generates. In most cases, there is a direct
relationship between bone mineral content (density) and
bone strength. In other words, the stronger the bone, the
more dense it is.

There are many studies that show that weight-trained
athletes have levels of bone mineralization that far exceed
that of untrained persons.

Doctors will also recommend to women to be active/lift weights to avoid osteoperosis. If that says anything...

C

As I understand it, general activity (such as walking)
increases bone density only for previously sedentary people.
Once a person reaches a minimum level of fitness, the
intensity of the exercise needs to be increased in order to
continue to stimulate bone density change.

In weight training, the factors that seem to be important with
respect to change in bone density are the load (weight), the
speed of contraction, and varying the direction of the load
(i.e., sometimes doing a squat, sometimes doing a deadlift).

For osteoporosis, exercises that load the hips and spine, like
back squats, deadlifts, and cleans are recommended.

Interesting. Thanks for the info

I aslo read what LEGION-X just said. I think maybe Dr. Fred Hatfield had it in his book power.

But for people like me who do only bodyweight exercises these days, how will that affect bone density?

I think that what Legion-X said more or less true for the spine,
but not necessarily true for other parts of the skeletal system.
Loaded exercises creates mechanical forces that stress the
bones; it's not quite like putting weights on a olympic bar and
watching it bend because we don't load our skeletal system
in that way during weight training.

Think of a biceps curl. As the biceps contracts, the force on
the bone comes from the strength of contraction of the
muscle. The biceps originates at one end of the humerus
(actually on the coracoid process of the scapula), and inserts
just below the elbow joint. As the biceps contracts under a
heavy load, this causes a slight posterior deformation of the
humerus. Osteoblasts move to the area of the bone
experiencing the greatest deformation. There, they lay down
collagen proteins that form a matrix. (I've never read about
the acid that Legion-X talked about.) Over time, minerals
bind to the matrix and mineralize, forming new and denser
bone.

I don't know for sure, but I would think that BW exericises
would not elicit the same effect in a fit person. There is a
threshhold stimulus that must be exceeded in order to
stimulate the process of bone formation. For a previously
sedentary person, BW exercises would probably give
sufficient stimulation. For a person who is already fit, I would
think that resistance training, jumping, and/or sprinting would
be required. But I would be interested to hear more
opinions...maybe the king of bodyweight exercises,
Scrapper, will chime in here.

The rate at which the bone is loaded is important as well.

In an interesting study, women wore weighted vests over a period of nine months, with the weight progressively increasing, no change in bone density was noted.

However, athletes such as volleyball players, who consistantly, quickly and heavily load their bones demonstrate the greatest bone density.

So plyometrics seems to be the best (best rate of loading) but weight training near maximum will probably help as well.

Well bodyweight exercises ARE resistance exercise so i dont see how there would be any difference in how the bones would react than to weights.

Yep, you just need to get the resistance up to the same level. Your body doesn't know if it's lifting itself, or weights. It can't tell the difference.