Monday, April 22, 2013

Bone lengthening in response to stress?

Presented are the findings that tennis players do have longer stroke arms than the contralateral arm.  This does not seem to be due to a selection bias as the mean contralateral arm of the tennis player is the same as the control arm for non-players.  Thus there does not seem to be a selection bias for arm length as there does for say basketball and height.

The changes in the tennis player seem to be throughout the entire bone rather than just the ends of the bones.  If the changes were due to the growth plate you'd expect the changes to be constrained to near to the ends of the bones but since the changes are throughout the entire bone it's more consistent with plastic deformation.

However, the changes in bone length are small and it's hard to create a serving/throwing motion with your legs or spine.  And the studies are not perfect for our purposes as we'd want to look at more longitudinal studies and people without present growth plates.

This still provides evidence that very high forces could generate active tensile induced longitudinal growth in bone.  However, the difficult in reproducing the throwing/serving motion in other bones and the relatively minor amount of growth in general means that such a method is not a practical method of gaining height.

Basepall pitcher's pitching arm tends to be longer than their non-pitching arms.  Many have speculated that this may be due to the stress that pitching arm undergoes.  However, many have retorted that people with one arm longer than the other may just be better pitchers.  That problem does not exist with instrument players.  Longer fingers do not make people better guitar or violin players.

I found this as a science fair project for the California state science fair.  Looks like students are the only ones willing to do height increase research thanks to the fact that grow taller is a dirty phrase.

The Fingers of Isaac Stern: Will Constant Stress Affect the Development of Phalanges?

Here's a page that considers a similar project.

The objective is to determine if violinists have longer phalanges in their left hand than their right hand compared to non-violinist. I believe violinists have longer left hand fingers due to the stress on the bones.
Methods: 6 steps: 1)Design a questionnaire 2)Define samples. 3)Select two groups: violinists and control group,each with twenty four people,divide evenly into four sub-groups: male, female, adult and young adult.(12 & up) 4)Define uncontrolled variables. 5)Conduct a personal interview and measure the index, middle, ring finger & pinky. 6)Analyze data.
Materials: A specially made ruler is used. It has a moveable piece of cardboard on the ruler for easy reading and maximum accuracy.
The violinist group has much longer phalanges in their left hand by as much as 0.6 cm. The non-violinists left hand four fingers are significantly shorter than the right hands' by as much as 0.9 cm. The data show no significant difference between both adults and young adults, male and female group.
Conclusions: My hypothesis is correct. The violinists' left hand fingers are longer than their right hand. This might be due to the stress they put on their bones during years of practice.
Next question: I would like to know if my research would help any medical study. Especially for the handicapped with two legs of different length.

Now, unlike the baseball pitcher, longer fingers do not make for better violin players.  The non-violinists had longer fingers in their right hand and since most people are right handed, using a hard more would indicate finger length.  There is still the possibility that left handed people may be better violin players and that left handed people have longer left hands that right hands.

What is interesting is that playing the violin there are no microfractures and there are no epiphyseal distraction forces.  The phalanges are long bones in the finger.  The mechanism as to how playing the violin would result in long bone lengthening is unknown.  One would wonder what the effect of bone lengthening would be in regards to typing which puts the same kind of stresses on finger bones, doesn't select versus right or left hand(okay qwerty is more left handed and dvorak is more right handed), and also doesn't cause microfractures or major distraction forces.

Unfortunately this one kids research paper is the only piece of information I could find on the subject.  Hopefully this kid will became an important scientist and help us find way to grow taller naturally.

According to this article guitar makes your fingers longer:  "Playing guitar does make the fingers of a fretting hand longer"  There are other articles that say otherwise.

According to this publication playing guitar/violin does increase finger length

Do the “Spreadability” and Finger Length of Cellists and Guitarists Change Due to Practice?

"It is a widely held opinion among musicians that extreme joint positions increase the flexibility in the corresponding joints. There are also occasional views that extensive use of the fingers starting in childhood may lead to increased finger length. These opinions have implications for teaching methods; however, in spite of extensive examinations of the shapes of musicians’ hands, to date there have been almost no objective findings. There have been large-scale examinations of the angle of supination of the left elbow of violinists, with the finding that primarily genetic factors are responsible. In order to answer the question whether external factors can influence joint configurations of the hand as well as finger length, the active finger spreads and finger lengths of 210 subjects (cellists, guitarists, and control subjects) were measured. The working hypothesis was that there would be an increase in finger spread in the left hand fingers compared with the right if the frequent extreme positions taken on the fingerboard did in fact influence finger spread. The nonmusician control group, however, would not be expected to show this difference, or at least not to the same extent as in the musicians. Similar differences should apply to finger length, if this is influenced by long-term practicing on these instruments. A majority of the measurements of all three groups demonstrated a greater spreadability of the fingers of the left hand than of the right. In contrast to the comparison groups, there was a significantly greater span between the left hand index and small fingers of cellists. This span was not measured in the guitarists because it does not apply in their playing as it does for cellists. In addition, the measurements of the right-left differences in the finger lengths of the cellists when compared with the nonmusician group showed significantly longer fingers on the left than the right. This difference is probably caused by better-developed fingertips of the cellists. Further research is needed to discern whether the spreadability could be improved through specific training programs."

<-so they give a non-bone lengthening related possibility i.e. fingertip thickness.  But the science experiment phalanges themselves were actually longer.

Mechanical stresses and endochondral ossification in the chondroepiphysis.

"The ossific nucleus appears in an area of high shear (deviatoric) stresses; The edge of the advancing ossification front (zone of Ranvier or ossification grove) also experiences high shear stresses; and the joint surface, where articular cartilage forms, is exposed to high-magnitude hydrostatic compression. Intermittently applied shear stresses (or strain energy) promote endochondral ossification and that intermittently applied hydrostatic compression inhibits or prevents cartilage degeneration and ossification."

LSJL likely applies both types of stresses which is why it is both pro-chondrogenic and pro-endochondral ossification.

"Pressure caused cartilage formation in the perichondrium and periosteum as did tensile stresses acting at right angles to the perichondrium fiber direction."<-Note that the mature periosteum can form cartilage and not just the developmental perichondrium.

"Pressure and tensile stresses imposed on cartilage caused the “disintegration of the hyaline substance and its replacement by a fibrillar system”"

"adventitious cartilage arises in response to intermittent pressure and tension accompanied by movement. Immobilization caused the transformation of this cartilage into “bonelike” tissue."

"mechanical pressure and avascularity have similar effects in that both conditions favor differentiation
of cartilage rather than bone from precursor cells."

"Deviatoric (distortional or shear) stresses cause material distortions with no change in volume. Dilatational (hydrostatic) stresses are pure hydrostatic (compression or tension) stresses that do not distort but will cause volume changes if the material is compressible. The stored strain energy is the sum of the deviatoric and dilatational energy. Materials like cartilage, which are nearly incompressible, will store negligible dilatational energy since negligible volume change occurs, regardless of the magnitude of the dilatational stress. In such materials, therefore, the shear stress distributions will reflect the distribution of strain energy density."

"deviatoric stresses (which are accompanied by elongation or tensile strains in some direction) [are] a specific stimulus for the development of collagenous fibrils and hydrostatic pressure [is] responsible for chondrogenesis."

"The vascular supply pattern to the femoral head was found to correlate with regions that were not exposed to high magnitudes of intermittent hydrostatic compression."

Hydrostatic stress places stress more directly into the epiphysis of the bone than other forms of stress.

Short-term and long-term site-specific effects of tennis playing on trabecular and cortical bone at the distal radius

"Epiphyseal bone enduring longitudinal growth showed a great capacity to respond to mechanical loading in children"

"In children, no significant difference was observed between the dominant and nondominant forearm lengths (21.6 cm on both sides). In adults, the respective values were 25.3 ± 1.6 cm and 25.0 ± 1.6 cm, with a significant side-to-side difference"

Stimulation of Bone Growth Through Sports: A Radiologic Investigation of the Upper Extremities in Professional Tennis Players

"Can any differences be found in longitudinal growth of the bones of the forearm and hand in professional tennis players between the stroke arm and the contralateral arm? An investigation
was conducted involving 20 high-ranking professional tennis players (12 male and eight female players) between 13 and 26 years of age as well as 12 controls of the same age range. [Examination] of the bones of the forearm and hand yielded an increase in density of bone substance and bone diameter as well as length in the stroke arm as compared with the contralateral arm. This change in bone structure and size can be attributed to mechanical stimulation and hyperemia{increase in blood flow} of the constantly strained extremity."

"Significant difference in ulnar length between the two arms in the tennis players [ranging] from 0.2 to 1.3 cm"

The mean difference in ulna length in control group was 0.17mm but this could be a correlational rather than causal relationship.  People with a dominant longer arm may select tennis as a sport.

The mean length for the contralateral arm was 270mm which was the same as the control group but the mean length for the stoke arm was 278mm.

They also found an increase in the length of the second metacarpal of the playing arm of the hand of 4.1mm.  Average lengthening of the second metacarpal was 2.7mm.

In all likelihood, I think it's more likelihood that the tennis caused the overgrowth rather than being a correlational effect.

The phenomenon of twisted growth: humeral torsion in dominant arms of high performance tennis players

There's a lot of stuff in this article about the physics of the forces generated during a serve.

"twisted humeral geometry at different stages of development could be attributed to muscle forces inducing a torsional load."

"characteristic twisted bone growth profile was found in tennis players, baseball pitchers and handball players."

"Predominant axial loading by deltoid induces humeral hypertrophy with pronounced bone growth along the longitudinal axis."

"During ball impact, muscle forces are aligned with the longitudinal axis of the humerus."

"During the serve, the entire upper limb is subject to tremendous loads"

Right arm versus left arms of professional tennis player.  You can kind of see a twisted nature of the bone and the twist seems to go throughout the whole bone and not just the growth plate region.

According to Humeral torsion and passive shoulder range in elite volleyball players, "the dominant arm [is] on average 9.6° more retroverted than the non-dominant arm" for volleyball players.

Interesting no significant different in the epiphysis on the torsion side.  The trabeculae became angled.  After a period of no torsion the angled trabeculae become removed.

Longitudinal bone growth between the two seemed to be equal.

Effect of Starting Age of Physical Activity on Bone Mass in the Dominant Arm of Tennis and Squash Players

"To determine in female tennis and squash players the effect of biological age (that is, the starting age of playing relative to the age at menarche) at which tennis or squash playing was started on the difference in bone mineral content between the playing and nonplaying arms."<-this will help us know if torsional forces can increase bone height in adults.

"Bones of the playing extremity clearly benefit from active tennis and squash training, which increases their mineral mass. The benefit of playing is about two times greater if females start playing at or before menarche rather than after it."

According to Long-term unilateral loading and bone mineral density and content in female squash players, "The bone changes are greatest in the humerus which gives us some hints on what loading is beneficial torsional.

Bone Modeling Response to Voluntary Exercise in the Hindlimb of Mice

"The functional adaptation of juvenile mammalian limb bone to mechanical loading is necessary to maintain bone strength. Diaphyseal size and shape are modified during growth through the process of bone modeling. Although bone modeling is a well documented response to increased mechanical stress on growing diaphyseal bone, the effect of proximodistal location on bone modeling remains unclear. Distal limb elements in cursorial mammals are longer and thinner, most likely to conserve energy during locomotion because they require less energy to move. Therefore, distal elements are hypothesized to experience greater mechanical loading during locomotion and may be expected to exhibit a greater modeling response to exercise. In this study, histomorphometric comparisons are made between femora and tibiae of mice treated with voluntary exercise and a control group. We find that femora of exercised mice exhibit both greater bone growth rates and growth areas than do controls. The femora of exercised mice also have significantly greater cortical area, bending rigidity, and torsional rigidity, although bending and torsional rigidity are comparable when standardized by bone length. Histomorphometric and cross-section geometric properties of the tibial midshaft of exercised and control mice did not differ significantly, although tibial length was significantly greater in exercised mice. Femora of exercised mice were able to adapt to increased mechanical loading through increases in compressive, bending, and torsional rigidity. No such adaptations were found in the tibia. It is unclear if this is a biomechanical adaptation to greater stress in proximal elements or if distal elements are ontogenetically constrained in a tradeoff of bone strength of distal elements for bioenergetic efficiency during locomotion"

"Most mammals exhibit limb tapering with greater muscle and bone mass concentrations proximally, and thinner, elongated elements distally"

"bone may primarily be added periosteally to increase resistance to bending with new growth diminishing distally along the proximodistal axis"

They hypothesize: "Bone growth in response to loading will be greater in the femur than tibia to minimize the addition of bone mass distally."

"Twenty virgin female house mice (Mus musculus) of the inbred strain C57BL/6J were used in this experiment"

"The femora of exercised mice have significantly larger areas of bone growth both periosteally and endosteally than controls"

That is a huge difference in length.  Like 10%.

"exercise-treated mice ran an average of 7.8 km/day with a standard deviation of 1.19 km/day during the 4-week experiment."


  1. As a bodybuilder, I have often heard that pullovers, in addition for their muscle-building potential, create enough stress to physically expand the ribcage giving bodybuilder's a massive barrel-like chest. A good experiment would be to compare and contrast a bodybuilder's ribcage, who has performed many pullovers, to that of a non-bodybuilder of similar age via x-rays to see if the architecture of the bones are different enough to be credible.

    1. wow never heard that before and do you think it could be repetitive train or shear amounts?

  2. This project is interesting... I myself am a violinist and I found myself reading this article. It is true, we have longer left fingers due to putting stress on the string to produce a higher sound. Even after only a few years of playing, there is definately a size difference. Not many people look into the finger lengths of others. This must make for a very interesting science project. I found this to be enlightening and it got me curious. Yes we have longer left fingers, not as much in our thumb, however, but this was an interesting thing to look into. I hope this student got a good grade.

  3. so is it a repetitive movement or shear strain that causes this?

  4. One might also wonder if this sort of growth might be due to small but frequent vibrations. The violin would obviously cause a lot of vibrations just to make sounds, and tennis players would send consistent shocks of vibrations through their arms every 3 to 5 seconds of playing.

    Ive heard a similar thing about the hands of guitar players. I would not be surprised if this turns out to be a mechanical response of bone cells to being shaken up.

  5. tyler look this, please:

    nitric oxide is very bad, N.O are anti-chondrogenic !!!