Exercise Strengthens Bone Structure

[Guest guest]

I think it's important for the 'minimal exercise' crowd to consider

that too little exercise (especially true of non-weightbearing) may

not be enough to promote this bone adaptation. I don't know what that

threshold might be though..

Cells Tissues Organs. 2008 Aug 15. [Epub ahead of print]

Exercise Alters Mineral and Matrix Composition in the Absence of

Adding New Bone.

Kohn DH, Sahar ND, Wallace JM, Golcuk K, MD.

Department of Biologic and Materials Sciences, University of

Michigan, Ann Arbor, Mich., USA.

The mechanical properties of bone are dictated by its amount,

distribution and 'quality'. The composition of the mineral and matrix

phases is integral to defining 'bone quality'. Exercise can

potentially increase resistance to fracture, yet the effects of

exercise on skeletal fragility, and how alterations in fragility are

modulated by the amount, distribution and composition of bone, are

unknown. In this investigation, the effects of exercise on the size,

composition, mechanical properties and damage resistance of bones from

mice of various ages, background strains and genetic makeup were

assessed, as a means of testing the hypothesis that mechanical loading

can improve skeletal fragility via compositional alterations. C57BL/6

mice (4-month-old males) ran on a treadmill for 21 days. Tibiae from

exercised and control mice were analyzed for cross-sectional geometry,

mechanical properties, microdamage and composition. Exercise

significantly increased strength without increasing cross-sectional

properties, suggesting that mechanical stimulation led to changes in

the bone matrix, and these changes led to the improvements in

mechanical properties. Consistent with this interpretation, the

mineral/matrix ratio was significantly increased in exercised bones.

The number of fatigue-induced microcracks was significantly lower in

exercised bones, providing evidence that exercise modulates fatigue

resistance. The ratio of nonreducible/reducible cross-links mirrored

the damage data. Similar trends (exercise induced increases in

mechanical properties without increases in cross-sectional properties,

but with compositional changes) were also observed in 2-month-old

biglycan-deficient and wild-type mice bred on a C57BL/6x129 genetic

background. S. Karger AG, Basel.

PMID: 18703871

[Guest guest]

in other words...

" Use it or lose it!! "

-CRT

--- bill4cr <bill4cr@...> wrote:

> I think it's important for the 'minimal exercise'

> crowd to consider

> that too little exercise (especially true of

> non-weightbearing) may

> not be enough to promote this bone adaptation. I

> don't know what that

> threshold might be though..

>

>

> Cells Tissues Organs. 2008 Aug 15. [Epub ahead of

> print]

> Exercise Alters Mineral and Matrix Composition

> in the Absence of

> Adding New Bone.

> Kohn DH, Sahar ND, Wallace JM, Golcuk K,

> MD.

>

> Department of Biologic and Materials Sciences,

> University of

> Michigan, Ann Arbor, Mich., USA.

>

> The mechanical properties of bone are dictated

> by its amount,

> distribution and 'quality'. The composition of the

> mineral and matrix

> phases is integral to defining 'bone quality'.

> Exercise can

> potentially increase resistance to fracture, yet the

> effects of

> exercise on skeletal fragility, and how alterations

> in fragility are

> modulated by the amount, distribution and

> composition of bone, are

> unknown. In this investigation, the effects of

> exercise on the size,

> composition, mechanical properties and damage

> resistance of bones from

> mice of various ages, background strains and genetic

> makeup were

> assessed, as a means of testing the hypothesis that

> mechanical loading

> can improve skeletal fragility via compositional

> alterations. C57BL/6

> mice (4-month-old males) ran on a treadmill for 21

> days. Tibiae from

> exercised and control mice were analyzed for

> cross-sectional geometry,

> mechanical properties, microdamage and composition.

> Exercise

> significantly increased strength without increasing

> cross-sectional

> properties, suggesting that mechanical stimulation

> led to changes in

> the bone matrix, and these changes led to the

> improvements in

> mechanical properties. Consistent with this

> interpretation, the

> mineral/matrix ratio was significantly increased in

> exercised bones.

> The number of fatigue-induced microcracks was

> significantly lower in

> exercised bones, providing evidence that exercise

> modulates fatigue

> resistance. The ratio of nonreducible/reducible

> cross-links mirrored

> the damage data. Similar trends (exercise induced

> increases in

> mechanical properties without increases in

> cross-sectional properties,

> but with compositional changes) were also observed

> in 2-month-old

> biglycan-deficient and wild-type mice bred on a

> C57BL/6x129 genetic

> background. S. Karger AG, Basel.

>

> PMID: 18703871

>

>