BIOMECHANICS AND KINESIOLOGY I Flashcards
(1) Without the aid of reference, identify bone tissue
behavior under stress without error. (0919-TRNG-2004v)
a. Bone. Bones provide structure to the body and serve as
attachment points for muscles.
(1) Composition and Structure. Bones are uniquely
designed and may harden with training and exercise.
(a) Storage: Bone serves as reservoir for essential
minerals in the body, especially calcium.
(b) Growth: Bones will grow longitudinally as long
as end plates are open. End plates may close at age 18.
(c) Bones are able to accommodate limited
deformation dependent on direction and magnitude of stresses.
(d) 25% weight of bone is water
(2) Loading & Stress Behavior. Stress can occur in a
variety of ways: tension, compression, sheer, bending, and
torsion. Below is a graph depicting the “Load – Deformation
curve.” The bone is more resilient when force is applied in the
longitudinal position and it’s resistance to stress decreases as
the stress approaches the transverse plane.
(3) Degenerative Changes in Bone Associated with Aging.
Progressive loss of bone is normal with aging.
(a) Age, gender, and body mass. All three of these
are factors in bone density.
(4) Muscle Activity on Stress Distribution on Bone.
Contraction of the muscle alters the stress distributed in the
bone. The muscle contraction decreases or eliminates stress
partially or totally.
(5) Fatigue of Bone under Repetitive Loading. Bone can
fracture by a single load that surpasses its ultimate strength
or by repeated load application of a load of lower magnitude.
As muscles fatigue, they are no longer able to absorb energy.
(2) Without the aid of reference, identify joint
structures without error. (0919-TRNG-2004w)
b. Joints.
(1) Structure. Joints may be classified by structure or
function. For the purposes of this class, we will focus on the
structure of joints.
(a) Fibrous: There is no cavity, or space, present between the bones, so most fibrous joints do not move at all.
Example: sutures in head (synarthridal).
(b) Cartilaginous: Cartilaginous joints are those
in which the bones are connected by cartilage. Example:
coracoclavicular joint, pubic symphysis, or costochondral joint of ribs (amphiarthridal).
(c) Synovial: Synovial joints are the only joints
that have a space between the adjoining bones. This space,
referred to as the synovial (or joint) cavity, is filled with
synovial fluid. Example: knee joint, hip joint, or shoulder
joint (diarthridal).
(2) Loading & Stress Behavior. Joints can roll, spin,
and glide. In a synovial joint, there is a combination of all
three
(3) Without the aid of reference, identify factors of
cartilage wear and degeneration without error. (0919-TRNG-2004x)
Cartilage. Cartilage is formed at the end of bone where
two ends are in contact. They distribute the load over a wide
area, which decrease the stress in the joint. It also allows
for movements with minimal friction and wear. Some cartilage in the body increases stability by deepening the joint.
(1) Structure. Cartilage is made of chondrocytes and
has 4 zones. Overall, cartilage is an isolated tissue without
nerve, blood supply, and lymphatic channels. Therefore, this
tissue does not heal or repair well.
80% of cartilage is water
(2) Lubrication of Cartilage. Lubrication is needed to
reduce friction of the joint and creates a thin barrier between bones. Nutrients are delivered to the cartilage by thelubrication to the cartilage surface.
(3) Wear and Degeneration. Wear and degeneration may
naturally occur over time but can be accelerated due to poor mechanics, form, or excessive exercise.
(a) Load: Cartilage is minimally affected with axial
load/ tension. However, sheer is not tolerated well.
(b) Stress: Like bone, repetitive stress can lead to
fatigue wear of the cartilage even when lubrication is present.
(c) Osteoarthritis (OA): Osteoarthritis of the joint
may result from cartilage wear and degeneration. The ends of bone lose their smooth contacts and become rough and inflamed
(4) Without the aid of reference, describe elastic vs
plastic regions of ligament/tendon behavior without error.
(0919-TRNG-2004y)
Tendons & Ligaments. Tendons, ligaments, and joint
capsules surround, connect, and stabilize the joint. Ligaments and joint capsules connect bone to bone. The function of the tendon is to connect muscle to bone for transmission of force.
(1) Composition and structure. Tendons and ligaments
are made of connective tissue.
(a) Vascular properties: Ligament and tendons have
limited vascular properties which affects the healing process.
They receive blood through peripherally.
(b) Order: Fibers are aligned in parallel which give them strength under tensile loads. Ligaments generally
sustain loads in one predominate direction.
(c) Stability: Specialized receptors are located in
tendons and ligaments which help with stability and
proprioception.
(2) Elastic vs Plastic Region. Upon stretching the
ligament or tendon they are able to resist load under tension.
At some point there is a “plastic region”, where the tissue no
longer is able to return to it’s normal length. Past that,
there is a point of failure where the tissue ruptures.
(3) Factors that Affect Biomechanical Properties of Tendons and Ligaments. Tendon and ligament properties can change due to a number of variables.
(a) Maturation and Aging: As we age ligaments and
tendons decrease their elastic properties.
(b) Mobilization and immobilization: Physical training has shown to increase strength and stiffness of ligaments and tendons. Immobilization has shown to decrease tensile strength in tendon and ligaments. Immobilization may have impact for several months to years on ligaments and tendons.
(c) Steroids: When corticosteroids are applied
after an acute ligament injury; ligament stiffness decreases,
energy absorption decreases, and the failure point decreases.
(d) Grafts: When a graft is used to repair or
replace a ligament, it will take about 1 year for the healing
process to complete. In theory, the graft should be stronger
than the other side. Due to compliance or early return to
training, the graft may actually have more laxity.
(5) Without the aid of reference, identify the types of
muscle contraction without error. (0919-TRNG-2004aa)
a. Composition and Structure. Muscles fibers have 4
characteristics: excitability, contractility, extensibility, and
elasticity. Muscle tissue has the capacity to respond to a
stimulus (excitable). Muscle tissue has the ability to shorten
and generate pulling force (contractible). Muscle tissue can be
stretched back to its original length (extensible). Muscle
tissue has the ability to recoil to original resting length
(elastic).
b. Types of Contraction.
(1) Isometric: Isometric contractions occur when there
is no change in the length of the contracting muscle. This
occurs when carrying an object in front of you as the weight of
the object is pulling your arms down but your muscles are
contracting to hold the object at the same level.
(2) Concentric: Concentric contractions are those which
cause the muscle to shorten as it contracts. An example is
bending the elbow from straight to fully flexed, causing a
concentric contraction of the biceps brachii muscle. Concentric
contractions are the most common type of muscle contraction and
occur frequently in daily and sporting activities.
(3) Eccentric: Eccentric contractions are the opposite
of concentric and occur when the muscle lengthens as it
contracts. This is less common and usually involves the control
or deceleration of a movement being initiated by the eccentric
muscle’s agonist.
(6) Without the aid of reference, identify the roles of
muscle during contraction without error. (0919-TRNG-2004ab)
Roles of Muscle.
(1) Agonist: The agonist in a movement is the muscle(s)
that provides the major force to complete the movement. Because
of this agonists are known as the ‘prime movers’. In the bicep
curl which produces flexion at the elbow, the biceps muscle is
the agonist. The agonist is not always the muscle that is
shortening (contracting concentrically). In a bicep curl the
bicep is the agonist on the way up when it contracts
concentrically, and on the way down when it contracts
eccentrically. This is because it is the prime mover in both
cases.
(2) Antagonist: The antagonist in a movement refers to
the muscles that oppose the agonist. During elbow flexion where
the bicep is the agonist, the triceps muscle is the antagonist.
While the agonist contracts causing the movement to occur, the
antagonist typically relaxes so as not to impede the agonist.
The antagonist doesn’t always relax though, another function of
antagonist muscles can be to slow down or stop a movement. We
would see this if the weight involved in the bicep curl was very
heavy, when the weight was being lowered from the top position
the antagonist triceps muscle would produce a sufficient amount
of tension to help control the movement as the weight lowers.
(3) Stabilizers: The synergist in a movement is the
muscle(s) that stabilizes a joint around which movement is
occurring, which in turn helps the agonist function effectively.
Synergist muscles also help to create the movement. In the
bicep curl the synergist muscles are the brachioradialis and
brachialis which assist the biceps to create the movement and
stabilize the elbow joint.
(7) Without the aid of reference, identify muscle and
force relationships without error. (0919-TRNG-2004ac)
Muscle and Force Relationships.
(1) Length-force relationship: This relationship is
between a muscle’s length and the isometric tension (force)
which it generates when fully activated.
(2) Force-velocity relationship: Being hyperbolic means
that the rate of change of force alters with changing velocity.
At low velocities, the rate of change of force is very high and
it drops off quickly with small increments in speed. At higher
velocities, the rate of change of force is quite low and alters
little with each incremental change in speed. The hyperbolic
force velocity relationship describes the relationship between
muscle force production and contractile velocity in single
muscles while shortening. Therefore it does not necessarily
explain the relationship between joint moments and joint angular
velocity, nor does it explain the relationship between muscle
force production and contractile velocity in single muscles
while lengthening.
(3) Force-Time relationship: The force generated by a
muscle is proportional to the contraction time: the longer the
contraction time, the greater the force developed.
(8) Without the aid of reference, identify muscle
effects without error. (0919-TRNG-2004ad)
e. Muscle Effects.
(1) Effect of pre-stretching: Muscle performs more work
when it shortens immediately after being stretched in the
concentrically contracted that than when it shortens from a
state of isometric contraction. Phenomenon is not only
accounted by elastic properties.
(2) Effect of temperature: Increases conduction velocity
and increases the frequency of stimulation in the neurological
system; therefore, increasing force production. Increases
greater enzyme activity of metabolism. Muscle fiber temperature
increases by blood flow (warm up) and production of heat from
metabolism. (contraction fiction)
(3) Effect of fatigue: If a muscle has adequate oxygen
supply and nutrients that can be broken down to ATP, it can
sustain itself. The frequency must be low enough where ATP can
synthesize at a rate to keep up with ATP breakdown during
contraction.
(a) If the frequency of stimulation increases and
outpaces the rate of replacement; muscle responses grow
progressively weaker.
(b) Fatigue is first observed by a lack of
coordination of movement and its effect in the increase loads of
the tissue.
(c) Skills of the individual decrease.
(d) Decrease in accuracy control and speed of
contraction, which may predispose an individual to injury.
