Kinematics: The description of movement in space without regard to the forces involved. Commonly
involves linear movement, angular movement and general movement. The five primary variables which
are:
1. Temporal (timing) of movement
2. Position or location
3. Displacement
4. Velocity and
5. Acceleration
Kinetics: The study of forces acting on body. With specific interest on what causes or tends to cause
motion. Common variables found in the study of kinetics are inertia, mass, force, moment of inertia and
moment of force.
Force: is the effect of one body on another which is needed to change the current state of an object. In
terms of injury, there are seven factors that can help determine injury to include: magnitude, location,
direction, duration, frequency, variability and rate.
Torque: the effect of a force that tends to cause a change in a body’s state of angular position or
motion, for which torque is measured by the force of a body times the distance from the axis of
rotation.
Kinetic Energy: the energy a body possesses by virtue of its motion, or for simple, energy of motion
which can either be linear or angular.
Potential Energy: energy of position or deformation. PE has two forms which are gravitational form
(positional), and deformational energy which is store in the body by virtue of its deformation.
Strain Energy: Deformational energy that is stored in a body by virtue of its deformation. Examples of
strain energy are a stretched rubber band, or a pole-vaulters bent pole.
Stress: The internal resistance to an axial load and are commonly classified as compressive stress of
tensile stress and is measured in pascals.
Strain: is damage to a musculotendinous unit and is measured in the change of dimension divided by
the unloaded dimension. (i.e. how much a body deforms in response to a given load)
Stiffness: measures the relationship between stress and strain.
Short Answer:
2. Injury permeates society and have been a salient topic of study throughout mankind. The study
of injury incorporates many disciplines, such as anatomy, mechanics, medicine, and engineering
while exploring the overarching perspective of injury commonly found in the economical,
psychological, safety, and health fields of study. Within each discipline, we can easily find
research that’s matches individual areas of study. The currently challenge is, “we know a lot of
facts – but we lack integrated answers” (Caine et al. 1996, p.1). It would do a disservice to
clients to use only one lens of consideration, for we know that an injuries impact on life is not
limited to anatomical structures, or the exploration of mechanics associated with injury. Injury
also may impede on a person’s psychological foundation or current economical status. In order
to fully understand mechanisms, impact, and recovery, researchers must continue to use an
interdisciplinary approach for successful consideration of MSK injury.
3.
External rotation with extension of knee, internal rotation and flexion. Inversion eversion,
dorsi/plantar flexion. When talking about timing of ankle and foot, if there is an timing
imbalance then we can create torsional stress to the lower leg (mi
4. In order to decrease the potential for injury at landing when jumping from a platform 1m above
the ground and individual should focus on bending of the knees and hips in order to increase the
time component of momentum. Landing on mat and air bag example. Increase the time
component (land soft) (same force, but increase time).
Work – change in total mechanical energy (kinetic, potential, and strain)
5. Passive structures, such as ligaments, are largely designed to withstand tensile stressors and
tend to be bound by the strength of the tissue. Muscle can be activated and thus regulates the
stiffness. Both provide stability but muscle provides active tolerance. Ligaments have a set
strength and fall somewhere on the spectrum. Muscle can modulate stiffness.
6. In bending the concave surface will undergo compressive stress, while the convex surface will
undergo tensile stress. Greatest stress is on the surface. The wider the area moment of inertia
the greater resistance. Balance beam but 2x10. 2” vs 10”. Failure usually occurs at the weakest
point. For example, in three-point bending, failure usually occurs on the convex side in the
middle on the surface. Cantilever bending is a compressive force, with failure at weakest point
overall. 3-point in the middle (ski boot), 4 points in weakest spot between forces.
For torsional (twisting) loading, the larger the radius of the shaft (inner radius vs outer radius),
the more resistance it creates. The stiffer the material the harder it is to deform. Torsion creates
sheer stressor throughout shaft and stress is correlated with radius of shaft, applied torque, and
polar moment of inertia, In addition it creates stress in the form of helical stress with tensile
stressors along the lines of stress, with failure following spiral stress lines. Failure usually occurs
when the distal portion of the bone is fixed and the proximal portion continues rotating.
Increase resistance but increasing outer wall and increasing inner radius.
7. Anisotropic: Material exhibiting a direction dependent tissue response to an applied force. An
example of this would be the femor experiences a compressive load. It can manage the load
better when being loaded the longitudinal access (cortical wall). We know that load is not
always uniaxial, and tissue do not always exhibit linear behavior. Thus we see viscoelastic
produce a stress-strain curve. Tendon, collagen, parallel rows which allows for elasticity.
Ligament has spiral crossing fibers that can occupy different bundles. Resist external loads from
multiple directions.
Viscoelastic: Tissue that can return to their original shape or configuration after a load is
removed and have strain rate dependent response to loading. If we increase the strain rate, we
increase the stiffness. The more we load, biological tissues begin to lose energy (hysteresis) and
if load goes above certain threshold, we start to see fatigue. When fatigue starts to set in,
tissues exhibit a decreased ability to withstand forces, which can lead to injury. Creep, stress
relax
8.
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