Researched
and Composed by
Jacob Wilson, BSc. (Hons), MSc. CSCS
Abstract
The following article is a continuation of the series on
bone mechanics. Once again it is placed in a questions and answers format.
What are the specific forces
that Bone Must Cope With, and How Is It Designed To Cope?
Today, I intend on introducing you to four specific
forces that each of your bones must face. This section will be referred to in
almost every single article dealing with the skeletal system, which follows.
Here is what I want you to know:
1. Four specific
forces, which occur on the skeletal system
2. When these stressors are manifested
3. How Bone Tissue is Constructed To
Accommodate Each Specific Situation
1.
Compression
When a system is “ squeezed “ it can be referred to as a
compression stressor( 36 ). Two bones being pressed tighter together is the
greatest example of such a case. For example, your femur articulates with your
tibia. When you stand, the condyles of those bones compressed against each
other. This stress is greater when under a load of resistance.
The most dealt with compression area is the vertebral column. This column is
composed of individual bones called vertebrae. They form joints, in a similar
manner as a chain of links would. It is for this reason that the “back bone” is
often referred to as the “posterior chain.” With great freedom comes great
responsibility, and such is the case with your vertebral column. Several
movements can take place within its parameters, including flexion( bending
forward ), extension, side bending, rotation( 21 ), etc. etc.
Vertebrae are stacked one on top of each other.
Specifically, one body of one vertebrae, lies on top of the body inferior to
it. Thus, as you sit in an erect position( at least that is preferable ), each
vertebrae bears the weight of the vertebrae superior to it. Actually, the
effects are additive, meaning the lumbar region( lower back ), must bare much
more weight then the cervical( neck ). Pressure is doubled when the area is
halved.
Therefore the body is designed with the lumbar region containing much wider
vertebrae then their cranial (closer to the skull cap) counterparts( 59 ).
Further, in order to absorb much of the shock, their lies a cushion of
cartilage, known as the annulus fibrosis( intervertebral disks ) between each
adjacent vertebrae.
When the body is properly aligned, it is interesting to note that it is designed
to use compression as a tool to actually “ stabilize “ itself. However, when
alignment is faltered, compression can and will have deleterious effects
(detrimental / injurious)(22).
In order to analyze the vertebrae, you must be familiar with the compression
forces born between two adjacent neighboring bones. You see, the body is not
the only aspect that articulates. In reality, there are four processes, which
protrude laterally on these bones called articular processes. Two inferior
articular processes of the superior( on top ) vertebrae, articulate with the two
superior processes of the inferior bone. When the vertebrae are pulled into a
state of flexion, all the weight is born by the adjacent bodies. However, when
in full extension, compression is born by both the bodies and the articular
processes. Therefore you minimize stress. As we will see in a future issue,
which analyzes this area in extreme detail, countless factors can affect this
relationship. Your goal as an athlete is to minimize stress, or in many cases
use it to your advantage. Other factors which you will learn about concern
intervertebral hydration rates. Meaning many of your actions can dehydrate the
annulus fibrosis. Meaning that compressive forces will exude that much greater
stress on the parties involved.
How Does The Body Cope With
Compression?
Several factors must be taken into consideration.
However the main players are
A. Bone Mineral Content – this refers to the total amount of mineral
within one specified bone(4, 9, 17 ).
B. Bone Mineral Density – How much mineral content can be found within a
region of bone. According to Dr. Barron in his study of mineral density, 80-90
percent of cortical bone is calcified, where as that figure is only in the 20-25
percent range for trabecular( spongy) bone( 4 ). As a consequence we would
therefore expect more fracture rates in regions of the body, composed primarily
of the latter (59). According to Dr. Highet in the Journal of Sports medicine,
the limbs( appendicular skeleton), are higher in percentage of dense cortical
then are the bones of the frame, that is-the axial skeleton( 25 ). It is for
this reason, that those who have aged, or not properly conditioned their bone
while weight training can easily fracture the spinal column, leading to such
disorders as kyphosis
(35, 20, 40 )(hunch back ).Interestingly enough, female athletes are at a major
risk of this, if they do not pay extra special care to several specific
factors(27).
C. Specified Cortical Strength – Think carrot. That may sound strange,
but it sets up the perfect analogy for understanding this aspect of bone
tissue. If you take a carrot, and bend it, you notice that the highest amount
of stress occurs on the outer edges of the root as it is being stretched, and
bent( compressed ) at the same time. On the inside, the pressures cancel each
other out (36). Therefore when you hear the root snap, it is due to the outside
aspects this particular system failing, and not the inner regions (or no where
near). Weight on your bones, normally occurs “ off center(36). “ Meaning, the
same effect is occurring. Thus, as wolfs law states, shape is related to
function (59). Therefore you can deduce that the outside of the bone would
contain a higher amount of cortical tissue. This is exactly what we find (25).
D.
Specified Trabecular Strength – Trabecular(
spongy bone ) strength can be thought of as being akin to structural beams. In
other words, where stress is great, spongy tissue on the inside of a bone is
greatest. Just as you would place more support on the side of the building
which bares the brunt of the structure. Once again, a flawless design (19).
The rest of the bone does not need as much support, and instead is hollow, and
filled with marrow.
As an athlete, you will therefore want to emphasize
activities, which enhance bone mineral content, and increase cortical width and
calcification( 18, 20, 19, 30, 31 ). Shortly, we will not only analyze this
from a training standpoint, but also nutritionally. Further, we must consider
every detrimental aspect, which can subtract from the desired effects.
2. Tension
Any type of “ pulling “ force, qualifies as a form of
tension. Two main pulling forces act on
bones. The first is based on what is called the “ musculotendon unit. “ This
comprises the joining of a tendon into a particular bony region. Thus, the
musculotendon unit distally for the biceps brachii is on the lateral bone of the
forearm, that is-the radius. As a muscle contracts its force is transferred via
this attachment point, and it is during this time where the aspect of insertion
is pulled. All forces have four unique characteristics. I will not go into
heavy depth on calculating them today, but I will in the future. The main
aspects I am concerned with today are magnitude and point of application. The
former refers to the amount of force applied, the latter refers to where the
force is applied to. Thus, the level at which the biceps contract, and its line
of pull effect the stress level on the bone. Though the insertion point cannot
be changed, the line of pull can
(24). Keep that in mind, as it has significant application for those attempting
to enhance speed and strength. Ligaments also exert a pulling force on the
bone.
The second main form of tension is opposite that of compression. Simply put, it
is the stretching aspect that occurs when you bend a carrot. The femur provides
an excellent illustration of why this is the case. It must bare all the weight
superior too it, and it is placed at an angel, which allows us to walk fully
upright.
How Does The Body Cope With Tension?
For the compression / tension relationship, it once again
has a greater density of cortical bone on its periphery. However, the musculo-tendon
relationship is different. You see, if the bone does not cope, your muscles can
literally pull the tendon right off your bone! Not a pretty picture eh? Bone
however is designed to grow where tension is greatest (59). Thus, the junction
between bone and tendon will be a rather large protrusion as is on the medial
and lateral epicondyles of the humerus. As you palpate this area, you will now
have a greater appreciation for the importance of high density bone, where it’s
needed most! There are times however when a muscle can increase in strength
faster then bone can handle it, and this is where injuries occur. One of the
main areas is during a growth spurt, or during a bulk. However, several
precautions can be taken, just like in any training regiment to “ maximize “
bone density, and completely avoid this (covered in part three).
3. Torsion
Supination is the process by which you twist your forearm
so as to turn your palm superiorly (facing upwards). Twisting dumbbell curls
take advantage of this motion by beginning with the palm turned downwards. As
one turns their wrist, the weight is actually resisting in the opposite
direction, thus the forearm bones are being twisted in opposite directions at
once. This is what is known as “ torsion. “ When Marshal Faulk stops and spins
the opposite direction, he has stressed his tibia( lower leg ) by exposing it to
this force.
How Does The Body Cope With
Torsion?
If you recall from article one, cortical bone is actually
composed of layers or circular rings of bone called lamellae. Collagen is what
gives a bone its strength. Once again, God has composed an amazing plan to cope
with such stressors. Each layer runs in the exact opposite direction throughout
an entire haversian system! This means that bone can take an extreme amount of
stress and keep coming for more (36).
4. Shearing Stress
When two bones slide past each other, the result, or
rather the process is known as shearing(22). For example, if an athlete bounces
on a preacher curl, his forearm will slide downwards while the humerus remains
in place. In football, when an player clips an opponent, their shin bone will
slide forward while the thigh remains steady.
How Does The Body Cope?
Similar to tension, in regards to tendon insertions, the bony formations where
ligaments attach must be extremely strong. If this is the case, then sliding
will be minimized.
Inventory List of Bones Mechanical Properties
To Recap, bone tissue’s mechanical properties can be divided into three specific
areas.
1. Elasticity – Like a rubber band, bone is
displaced. The capability to return to its original shape is known as
elasticity. This will be further discussed when addressing a concept known as
the “ stress – strain relationship. “
2. Strength – This tissue’s level of strength can be characterized as its
ability to fight fractures caused by any of the above four main levels of
stress. To give direct measurements, a healthy bone has half the strength of
steal in resisting compression, and when compared to withstanding tension it is
fully as strong as steel! Think about that next time you are under the rack!
3.
Fatigue Resistance – Stress fractures are a
common term these days (22). Essentially it refers to the process by which an
athlete fractures a bone by repeatedly using it on similar activities. A bones
ability to sustain activities for long periods of time is known as fatigue
resistance.
Each of the above factors is of vital importance, and can be manipulated (9).
You speak of Machinery, What
Specific Machines Are Formed By Bones?
Such a question merits extreme insight. Therefore my
intensions are to introduce you to various machines today, and dedicate
whole articles on more in depth functions of these concepts, and how to
manipulate them for maximum speed and strength in a future addition of
Hyperplasia.
In order to grasp this concept, I need to first explain what purposes, are
served by machinery.
Note: Not all of these are served by one
individual construction. However, each is able to fill one or more of the
following criteria
1. They have the ability to alter the direction that the force is
applied. In other words they can take a force that is directed one way, and
cause it to be transferred in another direction (11). A machine may for example
take a force that is directed posteriorly, and change the line of pull so that
the force is transmitted anteriorly.
2.
A Machine may have the ability to stabilize
two weights.
3. Of extreme importance is to provide the mechanism, whereby the force
you apply( i.e. muscular contraction ) can be manipulated to actually move a
greater resistance, then the force which was applied. This is a “ mechanical
advantage. “
4. To provide an advantage in movement. This means that a machine can
move load X, further then applied Force A did.
5. Finally a machine can provide an advantage in speed applicability.
That is-the ability to move a load faster then the applied force moved.
Bones in the human body are designed to form three specific machines. These
include the following.
A. The Lever System – This particular system consists of a fulcrum, also
known as an axis, and a lever which rotates around it. The axis is always
perpendicular to the plane, which the level moves. To illustrate this look at
your elbow joint, which is formed by the humerus, radius and ulna. This is
known as a hinge joint (21, 25). Now straighten the elbow joint and place it at
your side so that your palm faces forward. The axis runs side to side from the
medial aspect of the elbow to the lateral aspect. The movement of the lever
however brings the forearm closer to the arm( flexion ), or moves it further
away from the arm( extension ). As you can see this is perpendicular, or forms
a 90 degree angle with the axis. In a lever system, the general positive force
is muscle contraction. This can stabilize a load, or cause movement as
described. There are actually three lever systems, which will be detailed
latter. I will however describe a simple mechanical advantage currently. Think
of a hammer pulling the head of a nail out of a board. The point of application
is the end of the hammer on the nail. The axis, is an imaginary line running
through the point of rotation and is perpendicular to the action. The lever(
handle ) on the hammer allows the user( you ) to apply force further away from
the point of application. Recall from earlier in the article, that two keys to
determining stress on an object are the point of application, and the degree of
force. In order to determine how large the force is, you simply multiply the
force applied (as in a muscular contraction), Xs the force arm distance.
Therefore applying force higher up on the hammer handle, enhances the magnitude
of the force at the point of application.
Most levers in the body however provide advantages in speed, and range of
motion, such as the ankle joint. In this movement, the axis is the ankle
joint. The applied positive or motive force is the posterior calf muscles, and
the point of application is the ball of the foot when performing plantar flexion
(standing calf raises).
The main bones, which serve as levers are “long bones.” Long bones are just
that, longer then they are wide. Your thigh bone is a perfect example. The
joints formed are the basic fulcrums. However, many positions, which we will
analyze in the future, allow the entire body to work as a lever system.
B.
Wheel and Axle Machines - Such machines
provide maximum range of motion, and also tremendous abilities to enhance speed
production. They can also be used to increase the magnitude of torque. The
most basic wheel and axle machine to illustrate my point is a can opener. You
clip the blade into the can. Following this you twist the can opener handle,
which causes the blade to rotate around the can eventually freeing the contents
for your next meal. There are several points to make here. One, if you recall,
the measurement or length of the force arm( i.e. the handle of the hammer ) is
proportional to the magnitude of the torque produced. The same applies here.
However, in a wheel and axle system, the radius of the wheel, is the force arm.
The radius is simple to calculate. It is the length or distance of the point in
the middle of a circle, to its perimeter (or half the diameter).
In a wheel and axle system, the axle is the aspect, which
is of a smaller diameter. Thus, on the can opener, the resistance, which is
being overcome, is at the actual point on the can, which is being cut through or
opened. The small blade doing the cutting is the axle. The mechanical
advantage is provided by the wheel (handle) on the can opener because it has a
larger radius then the axle, allows a lesser force on the wheel to be
transmitted to a greater force at the point of application.
That is one arrangement. However, you should also
realize that roles could be reversed. If the wheel is the larger diameter
aspect of this machine, we know that if a force is applied to the wheel it will
have a larger torque (force through rotation), then will the axle, had you
applied the force directly to it instead.
Another key point however is that range of motion, and speed are increased on an
object with a smaller force arm. Roles are reversed Therefore, if you were to
apply direct force to an axle on a machine, you would actually turn the wheel
faster, then if you had applied that force directly to the wheel. Thus
a. Analyze the force applied. In the case of the human body, this is muscular
contraction. If that force is applied to a greater sized force arm, then the
magnitude of the muscle torque is increased.
b. If you decrease the radius, then you increase the speed and increase your
advantage in range of motion.
An excellent example in the body, which takes advantage of speed and range of
motion, can be seen through shoulder actions. Lets analyze this. The shoulder
joint is formed by the head of the humerus, inserting into the scapula. This is
called a ball and socket joint (25). And it allows the humerus to rotate.
Perform the following action. 1. Bend your forearm. 2. Now
cock it back as if you were going to throw a ball. 3. If you keep the
humerus in this plane, but rotate it forward, your forearm will move downwards
(similar to throwing actions). The rotation occurs on the humerus. If you
analyze the forearms movement however, you will notice that it rotated in a
circular motion, such that you could calculate its radius (the forearm was the
wheel as it was larger in diameter then the humeral rotation). The rotator cuff
muscles, and deltoids however applied their force to the smaller radius. That
is-the humerus or upper arm bone. This allowed for maximum speed build up, and
range of motion. But a disadvantage in the magnitude of force production. It
is more favorable to be able to utilize speed and ROM in this movement however(
think of a pitcher ). Therefore the machines in your body are specialized for
the tasks they must perform.
C. Pulley System – Out of all the machines housed
in our bodies, I have always been most intrigued with the pulley system
arrangement. Most people allow their lives to slip away, never realizing the
complex being that they truly are. Columbia Concise Encyclopedia defines such a
machine as follows:
“ A machine
consisting of a wheel over which a rope, belt, chain, or cable runs.
A grooved
pulley wheel like that used for ropes is called a sheave. A single sheave
mounted in a block and fixed in place changes the direction of force exerted on
the rope passing over it( 11 ).”
Columbia Concise 2003
Thus, a pulley system can change the direction of a
force. Think of the last time that you bit the dust. What protected your
knee? It was your patella correct (knee cap)? The patella not only provides
protection, but also acts as the wheel in your knee joints pulley system. You
see, your femur has two condyles, and these articulate with the condyles on your
tibia. The patella is placed in between the condyles. Finally, the tendon of
the quadriceps femoris forms within this bone. Any bone, which a tendon forms
within, is known as a “ sesmoid “ bone (21). When you extend your knees, the
quadriceps contract, but the muscles do so by pulling toward their center or
gaster. The pulley system in place here is the tendon (rope) with a tensile
strength of steel, and the sesmoid bone which it passes over. As the quads
contract, the pulley causes the force to be redirected so that the legs move in
the opposite direction, which is of course the action of extension.
Furthermore, the pulley system increases the magnitude of torque applied through
the knee joint (28, 52).
Can You Provide a Brief List
of Bone Categories + Functions?
Yes I can. And it will be quite easy now that we have
laid out the specific machinery found within the body.
Long Bones – As described
earlier these are longer then they are wide. Meaning the shaft encompasses the
majority of the tissue housed. The humerus, femur, forearm bones, leg bones
etc. are examples. Wolfs law states that shape is related to function (59).
Such is the case here. Bones with a longitudinal emphasis are used as levers.
The upper extremity bones are lighter, as they are used for a greater range of
motion, and actions such a manipulation of objects, and speed (a boxer throwing
a knock out punch). The femur and tibia are much thicker as they bare the
body’s weight. The fibula does not bare the weight of the body as it does not
form a joint with the femur and is therefore much smaller. However, due to
muscle attachments it is extremely bumpy, especially in the competitive athlete
(32).
Short Bones – As the name
implies, these are thick chunks of bone, which can primarily be found in the
feet and hands. What do you notice about both of these areas? They have
extreme movement correct. Indeed, the many joints, which can be formed between
short bones, allow for a high range of motion. Further more short bones are
used for elasticity and adaptability. When you walk the feet must bare extreme
amounts of weight, and conform to endless varieties of terrain. The arrangement
of this tissue in the region allows the feet to almost mold to these surfaces,
and absorb shock. This is why your feet have “ arches. “ Arches, which can be
manipulated to increase speed and storage of potential energy.
Flat Bones – Your skull
houses one of the most vital components of your central nervous system. The
brain. This area is composed of flat bones, which like a helmet or any type of
armor form protective barriers for their precious contents. The scapula is also
a flat bone (your shoulder blades), and protects several structures in the back
region.
Irregular Bones – Tissue
molded in the body that does not conform to the above shapes is known as
irregular bone. Your spinal cord is protected by these very bones. The
vertebrae have a shape which allows them to protect the CNS, provide canals
(foramen) for nerves to exit, have flat bodies and other processes for joint
formation, are designed for extreme forms of movement, and yet can bare extreme
amounts of weight( i.e. the lumbar region houses interlocking articular
processes, which allow an athlete to form the vital strong arch ). Additionally
they have processes such as the spinous processes (the back bone you can see
posteriorly ) and transverse processes which allow muscles to attach, and cause
localized rotations. Indeed, these are hand crafted for extreme situations and
a high array of environments.
Conclusion
The skeletal system is extremely complex, so then how does one manipulate this
for enhanced athletic performance? That is covered in part three of this
series.
Yours In Sport
Jacob Wilson
jwilson@abcbodybuilding.com
President Abcbodybuilding
/ Hyperplasia Magazine
References
1. Aarden EM,
Burger EH, Nijweide PJ. Function of osteocytes I bone. J Cell Bichem 1994;
55:287-299
2. Am J
Roentgenol Radium Ther Nucl Med. 1974 May;121(1):1-4. Review of roentgenographic
bone demineralization studies of the Gemini space flights
3. Arnold
Schwarzenegger, The Encyclopedia of Modern Bodybuilding, A fireside book
published by Simon and Schuster
4. Baron R.
Anatomy and ultrastructure of bone. IN: Favus MJ, ed. Primer on the Metabolic
Bone Diseases and Disorders of Mineral Metabolism. 2nd ed. New
York: Lippincott, Raven 1993:3-9
5. Beck, B.,
& R. Marcus: Osteoporosis in Men: The Effect of Gender on Skeletal Health. Sand
Diego: Academic Press, 129-155 ( 1999 )
6.
Biochemical changes in the collagen of human osteoporotic bone matrix. Connect
Tissue Res 1993: 29 119- 132
7. Knowlden,
Adam, Shock Yourself Out Of The Comfort Zone Three, Hyperplasia Magazine,
Copyright Abcbodybuilding 2003
8. Calvo M,
Kumar R, Health H. Elevated secretion and action of parathyroid hormone in young
adults ingesting high phosphorus. Clinical Endocrinology Metabolism 1988,
66:823-9
9. Colletti,
L. A., J. Edwards, L. Gordon, J. Shary, and N. H. Bell. The effects of
muscle-building exercise on bone mineral density of the radius, spine, and hip
in young men. Calcif. Tissue Int. 4: 12-14, 1989.
10. Collins
E, Norman A. Vitamin D. In: Malchlin LJ. Handbook of Vitamins, 2nd
ed. New York: Dekker, 1991: 59-98
11. Columbia
encyclopedia. Sixth edition. New York: Columbia University Press, 2003.
“Pulley.” The Columbia Encyclopedia, 6th ed. New York: Columbia University
Press, 2003
12. Damien,
E., J.S. Price, and L.E. Lanyon. The estrogen receptor's involvement in
osteoblasts’ adaptive response to mechanical strain. J. Bone Miner. Res.
13:1275–1282. 1998.
13. DeLuca
H. Vitamin D: 1993. Nutrition Today, November to December:6-11
14. Effects
of inactivity and exercise on bone. Physician and Sportsmedicine, 15, 91-97
15. Effect of weightlessness on mineral metabolism; metabolic studies on Skylab
orbital space flights. Calcif Tissue Res. 1976 Aug;21 Suppl:423-30.
16.
Faigenbaum AD, Strength training for children and adolescents. Clin Sports Med.
2000 Oct;19(4):593-619.
17. Frost,
H.M.: Vital Biomechanics: Proposed general concepts for skeletal adaptations to
mechanical usage. Calcified. Tissue International. 42:145-156
18. Frost
HM.Why do marathon runners have less bone than weight lifters? A
vital-biomechanical view and explanation. Bone. 1997 Mar;20(3):183-9.
19. God –
The Holy Bible
20.
Giangregorio L, Blimkie CJ. Skeletal adaptations to alterations in
weight-bearing activity: a comparison of models of disuse osteoporosis. Sports
Med. 2002;32(7):459-76
21. Gray,
Henry. Gray’s Anatomy, Descriptive and Surgical ( 15th edition ),
Barnes and Nobles Inc. 1995
22. Gregory
Haff, G. 2003: ROUNDTABLE DISCUSSION: Youth Resistance Training. Strength and
Conditioning Journal: Vol. 25, No. 1, pp. 49–64.
23. Gurd B,
Klentrou P. Physical and pubertal development in Young Male Gymnasts.
J Appl
Physiol. 2003 Jun 13
24. Hayes,
W.C. ( 1986 ) Bone mechanics: From tissue mechanical properties to an
assessment of structural behavior. In Y.C. Fung ( Ed. ), Frontiers in
Biomechanics, 196-209. New York: Schmid-Schonbein.
25. Hole,
Jown W. Human Anatomy and Physiology, ( 3rd edition ) Wm. Brown
Publishers
26. Huddleston AL, Rockwell D, Kulund DN, Harrison RB. Bone mass in lifetime
tennis athletes. JAMA. 1980 Sep 5;244(10):1107-9.
27.
Jacobson, P.C. W. Beaver, S.A. Grubb, T.N. Taft, & R. V. Talmage: Bone Density
and Women: College athletes and older athletic women. Journal of Orthopedic
Research. 2:328-332( 1884 )
28. John J.
Callaghan, John N. Insall, A. Seth Greenwald, Douglas A Dennis, Richard D.
Komistek, David W. Murray, Robert B. Bourne, Cecil H. Rorabeck, and Lawrence D.
Dorr, Mobile-Bearing Knee Replacement : Concepts and Results Journal of Bone and
Joint Surgery 2000 , Callaghan et al. 82 (7): 1020
29. Kannus,
P., H. Seivanen, and I. Vuori. Physical loading, exercise and bone. Bone.
18:1S–3S. 1996.
30. Kerr,
D., A. Morton, I. Dick, and R. Prince. Exercise effects on bone mass in
postmenopausal women are site specific and load-dependent. J. Bone Miner.
Res. 11:218–225. 1996.
31. Kohrt,
W.M., A.A. Ehsani, and S.J. Birge. HRT preserves increases in bone mineral
density and reductions in body fat after a supervised exercise program. J.
Appl. Physiol. 84:1506–1512. 1998.
32. Lanyon,
L.E. Using functional loading to influence bone mass and architecture:
Objectives, mechanisms, and relationship with estrogen of the mechanically
adaptive process in bone. Bone. 18:37S–43S. 1996.
33.
Lillegard WA, Brown EW, Wilson DJ, Henderson R, Lewis E. Efficacy of strength
training in prepubescent to early postpubescent males and females: effects of
gender and maturity. Pediatr Rehabil. 1997 Jul-Sep;1(3):147-57.
34. Lohman
T. Research related to assessment of skeletal status. In: Body Composition
Assessments in Youth and Adults. Report of the Sixth Ross Conference on Medical
Research. Columbus, OH: Ross Laboratories 1985, 38-41
35.
Manolagas SC, Jilka RL. Bone Marrow, cytokines, and bone remodeling: emerging
insights into the pathophysiology of osteoperosis. N Eng J Med 1995
36. Marrieb,
E.: Human Anatomy ( 5th edition ), Redwood City, Ca: Benhamin /
Cummings ( 2001 )
37. Mazess
RB. Dual energy x-ray absorbtiometry for the management of bone disease. Phys
Med Rehabil Clin North Am 1995; 6:507-537
38. Metcalf
JA, Roberts SO. Strength training and the immature athlete: an overview. Pediatr
Nurs. 1993 Jul-Aug;19(4):325-32.
39. National
Research Council. Recommended Dietary Allowances, 10th ed.
Washington, D.C. National Academy Press, 1989 124-84
40.
Notelovitz, M., D. Martin, R. Tesar, F.Y. Khan, C. Probart, C. Fields, and L.
McKenzie. Estrogen therapy and variable-resistance weight training increase bone
mineral in surgically menopausal women. J. Bone Miner. Res. 6:583–590.
1991.
41. Plowman SA, Liu NY, Wells CL. Body composition and sexual maturation in
premenarcheal athletes and nonathletes. Med Sci Sports Exerc. 1991
Jan;23(1):23-9.
42. Pocock,
N. A., J. A. Eisman, M. G. Yeates, P. N. Sambrook, and S. Eberit. Physical
fitness is a major determinant of femoral neck and lumbar spine bone mineral
density. J. Clin. Invest. 78: 618-621, 1986
43. Rausz
KGm Jrean BE. Regulation of bone formation, part 2 N Eng J Med 1883, 309, 83-89
44.
Regulation of Bone Formation, part 2 N Engl J Med 1983; 309:83-89
45. Rians
CB, Weltman A, Cahill BR, Janney CA, Tippett SR, Katch FI. Strength training
for prepubescent males: is it safe? Am J Sports Med. 1987 Sep-Oct;15(5):483-9.
46. Risser
WL, Lee EJ, LeBlanc A, Poindexter HB, Risser JM, Schneider V. Bone density in
eumenorrheic female college athletes.Med Sci Sports Exerc. 1990
Oct;22(5):570-4.
47. Rubin,
C.T., and L.E. Lanyon. Regulation of bone formation by applied dynamic loads.
J. Bone Joint Surg. 66:397–402. 1984.
48. Seksi,
Supplement Review – Calcium, Hyperplasia Magzine, April 2003. Copyright –
Abcbodybuilding
49. Skeletal
changes during space flight. Lancet. 1985 Nov 9;2(8463):1050-2
50. Snow-Harter, C., M., Boyxsen, B. Lewis, S. Charette, P. Weinstein, & R.
Marcus: Muscle Strength as a Predictor of Bone mineral density in young women.
Journal of Bone and Mineral Research. 5:589-595 ( 1990 )
51.
Sprynarova S. The influence of training on physical and functional growth
before, during and after puberty. Eur J Appl Physiol Occup Physiol.
1987;56(6):719-24
52. STUMBO, TERI A., MERRIAM, SARA, NIES, KARI, SMITH,
AMY, SPURGEON, DACOTAH, WEIR, JOSEPH P. 2001: The Effect of Hand-Grip
Stabilization on Isokinetic Torque at the Knee. The Journal of Strength and
Conditioning Research: Vol. 15, No. 3, pp. 372–377.
53. Termine
JD. Bone Matrix proteins and the mineralization process. In:Favus MJ, ed.
Primer on the Metabolic Bone Diseases and Disorders of Mineral Metabolism. 2nd
ed. New York: Lippincott, Raven, 1993: 21-25
54. Van de
Graaff, K.M., & S.I. Fox: Concepts of Human Anatomy and Physiology ( 2nd
edition ). Dubuque, IA, Wm. C. Brown ( 1989 )
55. Wardlaw G. Putting osteoporosis. Ann Rev Nutr 1984, 4 471-91
56. Wilson, Foster, Kronenberg, Larsen. Williams TextBook of Endocronology ( 9th
edition ) W.B. Saunders Company 1998
57. Wilson, Jacob, Is The All Or None Applicable To An Entire Muscle?
Hyperplasia Magzine, April 2003. Copyright – Abcbodybuilding
58. WITZKE, K. A. and C. M. SNOW. Effects of plyometric jump training on bone
mass in adolescent girls. Med. Sci. Sports Exerc., Vol. 32, No. 6, pp.
1051–1057, 2000.
59. Wolff, J Gesetz der
Transformation der Knochen. Berlin: Aug 1892
© ABC Bodybuilding Company. All rights reserved. Disclaimer
|
