Download Module 2- Biomechanics - Bangen Athletic Development

Module 2: Biomechanics
2.1 Skeletal and Muscular Systems
The skeletal system can be divided into two parts, the axial skeleton and the
appendicular skeleton. The axial skeleton includes the skull, spinal column, ribs and
sternum. The appendicular skeleton includes everything else (the shoulder complex,
arms, hips and legs).
Must Know:
Not every bone in the body needs to be memorized, as there are two hundred and
six of them. However, the location of the major bones of the body should be known.
These include:
 Phalanges (fingers and toes)
 Ulna (forearm, closest to the body in anatomical position/hands facing
forward)
 Radius (forearm, furthest from the body in anatomical position)
 Humerus (upper arm)
 Clavicle (collar bone)
 Cranium (skull/head)
 Mandible (jaw)
 Sternum and ribs (breast bone)
 Pelvis (hip, each side of which includes the ilium, ischium and pubis)
 Femur (thigh)
 Tibia (larger bone of the lower leg, medial to fibula)
 Fibula (smaller bone of the lower leg, lateral to tibia)
 Talus (ankle)
 Calcaneus (heel)
The bones of the spine are important to know as well. From the top of the spine
there are, in order:
 Seven cervical vertebrae
 Twelve thoracic vertebrae
 Five lumbar vertebrae
 Five sacral vertebrae (these are fused together)
There are three major types of joints, fibrous joints, cartilaginous joints and synovial
joints. Fibrous joints, such as the sutures within the skull, allow little to know
movement. Cartilaginous joints allow some movement and are found between the
vertebrae as intervertebral discs.
The joint type we are most familiar with are synovial joints (like the elbow or knee),
which allow considerable movement. Synovial joints can further be divided into
uniaxial (allow movement in one plane of motion such as the elbow), biaxial (allow
movement in two planes of motion such as the ankle) and multi-axial joints (such as
the hip which allows movement in all three planes of motion).
Major joints of the body:
Ankle- biaxial
Knee- uniaxial
Hip- multi-axial
Shoulder-multi-axial
Elbow-uniaxial
Wrist-biaxial
Must Know:
Like the skeletal system, there are too many individual muscles to memorize.
However, the location of the major muscles of the body should be known. These
include:
 Gastrocnemius and soleus muscles (calf muscles on posterior of lower leg,
responsible for ankle plantar flexion)
 Tibialis anterior (anterior of lower leg, responsible for ankle dorsiflexion)
 Quadriceps (includes vastus medialis, vastus intermedius, vastus lateralis
and rectus femoris, located on anterior of thigh, responsible for knee
extension)
 Hamstrings (includes semimembranosus, semitendinosus and biceps
femoris, located on posterior thigh, responsible for knee flexion)
 Gluteus maximus (located on posterior of hip, responsible for hip extension)
 Latissimus dorsi (located on back, responsible for shoulder horizontal
abduction, extension and adduction)
 Pectoralis major (located on chest, responsible for shoulder horizontal
adduction and flexion)
 Deltoids (includes posterior, medial and anterior, responsible for shoulder
flexion and abduction)
 Biceps brachii (anterior of upper arm, responsible for elbow flexion)
 Triceps brachii (posterior of upper arm, responsible for elbow extension)
Muscles attach in two positions, the origin and the insertion. The origin is the
proximal attachment, meaning that this attachment is closer to the center of the
body. The insertion is the distal attachment, meaning that this attachment is further
away from the center of the body.
During a movement, muscles can perform one of three roles:
Agonist: the primary mover of the exercise, during a biceps curl this role would be
served by the biceps brachii muscle.
Antagonist: the muscle that directly opposes the movement, during a biceps curl this
role would be served by the triceps brachii muscle.
Synergist: the muscle(s) that function either as secondary movers (muscles that aid
in the movement) or stabilizers (muscles that stabilize the joints surrounding the
moving joint), during a biceps curl the secondary mover includes the brachialis
muscles and the stabilizers include the muscles that surround the shoulder and
wrist joints.
2.2 Anatomical Planes and Movement
Anatomical position is defined as standing upright with the hands at the sides with
the palms facing forward. All movements are described from this position.
The sagittal plane cuts the body into right and left halves, the frontal plane cuts the
body into posterior and anterior halves and the transverse plane cuts the body into
top (superior) and bottom (inferior) halves.
Common Question:
What plane of motion is a movement performed in?
 Sagittal plane movements include any forward, backward, vertical or
downward motions. Includes running, jumping, squats and bench press.
 Frontal (coronal) plane movements include any side-to-side or lateral
motions. Includes jumping jacks, side shuffles and dumbbell lateral raises.
 Transverse plane movements include any rotational movements. Includes a
golf or baseball swing and any twisting motions.
Must Know:
Movement
Definition
Joint(s)
Flexion
Angle between bones increases
Extension
Angle between bones decreases
Abduction
Adduction
Left Tilt
Movement away from the mid-line
Movement toward the mid-line
Movement away from the mid-line
of the body to the left
Movement away from the mid-line
of the body to the right
Rotational toward the mid-line
Knee, hip,
shoulder,
elbow, lower
back and neck
Knee, hip,
shoulder,
elbow, lower
back and neck
Hip, shoulder
Hip, shoulder
Neck, lower
back
Neck, lower
back
Hip, shoulder
Rotation away from the mid-line
Hip, Shoulder
Transverse
Movement away from the mid-line
with the limb at ninety degrees
Movement toward the mid-line
with the limb at ninety degrees
Counter-clockwise rotation
Hip, Shoulder
Transverse
Hip, Shoulder
Transverse
Neck, lower
back
Neck, lower
back
Ankle
Transverse
Ankle
Sagittal
Right Tilt
Internal
Rotation
External
Rotation
Horizontal
Abduction
Horizontal
Adduction
Left
Rotation
Right
Rotation
Dorsiflexion
Plantar
Flexion
Clockwise rotation
Movement of the toes toward the
shin
Movement of the toes away from
the shin
Plane of
Motion
Sagittal
Sagittal
Frontal
Frontal
Frontal
Frontal
Transverse
Transverse
Sagittal
Ulnar
Deviation
Radial
Deviation
Inversion
Eversion
Movement of the hand toward the
mid-line
Movement of the hand away from
the mid-line
Movement of the foot toward the
mid-line
Movement of the foot away from
the mid-line
Wrist
Frontal
Wrist
Frontal
Ankle
Frontal
Ankle
Frontal
2.3 The Lever System
Movement occurs when muscle pulls on bone, rotating it about a joint. Another way
to look at it is that movement occurs when force acts on a lever about an axis
(fulcrum). The perpendicular distance between this axis and point of force
application is called the moment arm. Typically two forces acting on lever, they are
known as the force or effort arm and the resistance arm. As there are two forces,
there are also two moment arms.
As a lever is rotating about an axis, rotational force will be produced. This rotational
force is called torque, which is the product of the force and the moment arm.
Key Point:
Torque = Force x Moment arm
There are three types of levers:
 Type I - the force arm and resistance arm are on different sides of the
fulcrum.
 Type II- the resistance arm is between the force arm and fulcrum.
 Type III- the force arm is between the resistance arm and fulcrum.
Type I Lever
Type II Lever
Type III Lever
Mechanical advantage is the ratio of the moment arm through which an applied
force acts to that through which a resistive force acts. A mechanical advantage
greater than 1.0 allows the applied (muscular) force to be less than the resistive
force in order to produce an equal amount of torque. A mechanical advantage of less
than 1.0 is a disadvantage and requires the applied force to be greater than the
resistive force to produce an equal amount of torque.
Key Point:
Type I levers can be mechanically advantageous or disadvantageous depending on
the length of the moment arms. Type II levers will always be at a mechanical
advantage because the force arm will always be greater than the resistance arm.
Type III levers will always be at a mechanical disadvantage because the resistance
arm will always be greater than the force arm.
Mechanical advantage can be increased in two ways: increase the length of the force
arm, or decrease the length of the resistance arm. Strength differences between
individuals with similar training backgrounds and muscle mass can be accounted for
due to differences in tendon insertion. Those with tendon insertions further away
from a joint can produce less muscular force to produce the same amount of torque.
During real world movements both the resistance and force arm will change
through the range of motion. For example, during a biceps curl both the
perpendicular distance between the center of mass of the dumbbell and the elbow
joint and the perpendicular distance between the elbow joint and biceps tendon
insertion will increase from the bottom of the movement until the elbow is at ninety
degrees and will decrease from this point to the top of the movement. Therefore the
mechanical advantage of this lever will continually change throughout the range of
motion.
The position of the movement where the mechanical advantage is the lowest is
referred to as the “sticking point”. It is in this position where the muscular force
must be the greatest in order to produce enough torque to continue the movement.
The human body has evolved some structures to improve its mechanical advantage.
For example, the patella causes the force arm to produce more torque by increasing
the perpendicular distance between the quadriceps tendon and the knee joint.
Without the patella, the knee joint would have to produce much more force during
knee extension.
Most of the joints of the human body are third class levers. Therefore, most of the
movements humans perform are at a mechanical disadvantage. However, the need
to produce more muscular force to overcome external resistance does come with a
distinct benefit. Because the resistance arm is always greater than the force arm,
small displacements of the force arm while cause larger displacements of the
resistance arm. In other words, a small change in muscle length leads to big changes
in joint or limb position. This lack of mechanical advantage actually results in a large
speed advantage.
Resistance machines sometimes use cam levers that will alter the pattern of
resistance arm length throughout the range of motion.
2.4 Resistance Systems and Injury Prevention
To describe movement, the variables of force, work and power are used. Force can
be derived from many sources (see below). Work is used to quantify the amount of
force needed to complete a movement, or series of movement. Work is the product
of force and distance (W = F x d). Power is the rate of work (P = W / time or P = (F x
d) / time) and can also be expressed as the produce of force and velocity (P = F x v).
Gravity is the most common source of resistance, or force in strength and
conditioning and is utilized during bodyweight, free weight and weight stack
training. In this context force is the product of mass and acceleration (F = m x a).
This dictates that overcoming inertia, or changing the speed of a mass (whether
from a static position or after already moving) requires additional force.
Friction is another resistance source and can be observed during sled pushes or
moving one surface over the other. The force needed to overcome friction is derived
from the normal force of the object (the vertical line of mass) and the coefficient of
friction (k) (F = F(n) x k). The coefficient of friction is based on the roughness of the
surface. Ice would have a low coefficient of friction and pavement would have a high
coefficient of friction.
Two other common forms of resistance that are found in resistance training
equipment are fluid and elastic resistance. Both of these involve variable resistance
in which velocity (fluid resistance) and distance (elastic resistance). The force
produced through fluid resistance is a product of velocity and a constant, k, that is
based on the viscosity of the fluid (F = v x k). The force produced with elastic
resistance is a product of an elastic coefficient of resistant, k, and the distance the
elastic is stretched (F = d x k).
Common areas of injury during training are the shoulders, knees and lower back.
The shoulder is prone to injury during weight training because of its structure and
the forces to which it is subjected. Shoulder injury risk can be reduced by
performing a warm up with relatively light weights, following a program that
exercises the shoulders in a balanced way and exercising at a controlled speed.
The knee is prone to injury because of its location between two long levers. To
prevent knee injuries one should always perform a sufficient warm-up, utilize
appropriate loads and minimize the use of wraps to the heaviest sets.
The low back is the most common area of injury. Prevention steps include: flatten
the back during the lift to stabilize the lumbar spine (be sure not to hyperextend the
back), increase the intra-abdominal pressure to stabilize the spine. This can be
accomplished with conscious effort, use of a weight belt or with the valsalva
maneuver.
A weight belt should only be used for structural exercises (those that load the axial
spine directly such as squats or the deadlift) and only for heavy resistance sets (not
warm-up sets). The valsalva maneuver is performed by holding the breath in order
to create a fluid ball within the torso to stabilize the spine. Anyone who has high
blood pressure or CV disease should avoid the valsalva maneuver.
Must Know:
Reducing the Risk of Strength Training Injuries
 Perform one or more warm-up sets with relatively light weights, particularly
for exercises that involve extensive use of the shoulder or knee.
 Perform basic exercises through a full ROM.
 Use relatively light weights when introducing new exercises or resuming
training after a layoff of two or more weeks.
 Do not ignore pain in or around the joints.
 Never attempt lifting maximal loads without proper preparation, which
includes technique instruction in the exercise movement and practice with
lighter weights.


Performing several variations of an exercise results in more complete muscle
development and joint stability.
Take care when incorporating plyometric drills into a training program.
Stages of Tissue Healing
Inflammation (Occurs during the 2-3 days after the injury)
 Exhibited by pain, swelling, redness
 Decreased collagen synthesis occurs during this time
Repair (Occurs during the 2-3 Days to 2 Months after the injury)
 Collagen fiber production is the main healing process
 Stage is marked by decreased collagen fiber organization
 Decreased number of inflammatory cells shown during stage
Remodeling (Occurs during the 2-4 Months after injury)
 Proper collagen fiber alignment occurs
 Results in increased tissue strength
Common Question:
What is the rehabilitative strategy during each stage of tissue healing and what
other training can occur during the stage?
Inflammation Stage
 Goal of stage is prevention of new tissue disruptions and prolonged
inflammation with the use of relative rest and passive modalities
 Function of cardiorespiratory and surrounding neuromusculoskeletal
systems must be maintained by training other areas
 No active exercise for the injured area (for unaffected areas only)
Repair Stage
 Goal of stage is prevention of excessive muscle atrophy and joint
deterioration of the injured area
 Function of the neuromusculoskeletal and cardiorespiratory systems must
be maintained by training other areas
 Possible exercise options for injured area include:
o Submaximal isometric, isokinetic and isotonic exercise
o Balance and proprioceptive training activities
Remodeling Stage
 Goal of stage is optimization of tissue function
 Progressive loading of neuromusculoskeletal and cardiorespiratory systems
as needed (begin to integrate injured area)
 Possible exercise options for injured area include:
o Joint angle specific strengthening
o Velocity specific muscle activity
o Closed and open kinetic chain exercises
o Proprioceptive training activities
Module 2 Practice Questions
1. Which of the following is the best example of a multiaxial joint?
A. Ankle
B. Elbow
C. Hip
D. Wrist
2. During the toe off during a running stride, what is the function of the tibialis
anterior?
A. an agonist
B. a synergist
C. an antagonist
D. a prime mover
3. What is the mechanical advantage of a second class lever?
A. equal to one
B. greater than one
C. less than one
D. equal to one half
4. The anatomical plane that dissects the body into right and left halves is known as
which of the following?
A. sagittal plane
B. transverse plane
C. frontal plane
D. movement plane
5. Tom is working out with a free-weight training system. Which of the following
best describes the type of resistance he experiences as he exercises?
A. elastic
B. electronic
C. fluid
D. gravity
6. Margaret has severe edema and pain immediately following an injury. These are
signs of this phase of tissue healing:
A. inflammation
B. repair
C. remodeling
D. return
7. Dwayne is pushing a plate weight across the rubber floor of the weight room.
Which form of resistance is he utilizing during this exercise?
A. electronic
B. gravity
C. elastic
D. friction
8. Bob applied 100 newtons of force to a sled over 20 yards in a time of 10 seconds
and Tom applied 50 newtons of force for 30 yards in a time of 15 seconds. Who
produced the most power?
A. Bob
B. Tom
C. They produced the same amount of power
D. There is not enough information to answer this question
9. Which of the following axis of rotation in a first class lever?
A. fulcrum
B. lever
C. moment arm
D. force arm
10. How would you describe the lever system in which the muscle and resistive
forces act on the same side of the fulcrum and the moment arm of the resistive force
is longer than the moment arm of the muscle?
A. first class lever
B. second class lever
C. third class lever
D. all of the above
11. Jack has suffered a knee injury. In which phase of healing is it recommended that
he begin sport-specific movements and speeds?
A. inflammation phase
B. repair phase
C. remodeling phase
D. any of the above
12. The long jump primarily takes place in which anatomical plane?
A. sagittal
B. frontal
C. transverse
D. static
13. Which movement is the knee making during the downward phase of the front
lunge?
A. extension
B. flexion
C. abduction
D. adduction
14. Which of the following joint movements takes place in the transverse plane?
A. flexion
B. adduction
C. extension
D. horizontal adduction
15. Which of the following examples would increase the speed advantage of a
muscle?
A. increasing the muscular force
B. decreasing the perpendicular distance between the joint and the tendon insertion
C. increasing the resistance
D. increasing the perpendicular distance between the joint and the tendon insertion
16. What happens to the force required to move an elastic band as the band is
stretched?
A. decreases
B. remains the same
C. increases
D. becomes nothing
17. During which stage are the only exercises allowed are those that will not affect
the injured limb?
A. inflammation stage
B. repair stage
C. remodel stage
D. reuse stage
18. Which of the following upper leg muscle groups and types of muscle actions are
associated with the upward phase of the face down lying leg curl exercise?
Primary Muscle Group
Primary Muscle Action
I.
flexors
eccentric
II.
extensors
eccentric
III.
flexors
concentric
IV.
extensors
concentric
A. II and III only
B. I and IV only
C. I and III only
D. II and IV only
19. Which of the following is an example of a uniaxial joint?
A. ankle
B. hip
C. thumb
D. knee
20. Which of the following would involve a cartilaginous joint?
A. the joint between the femur and the fibula
B. the joint between two plates of the skull
C. the joint between two cervical vertebrae
D. the joint between the humerus and the shoulder girdle
Module 2 Practice Question Answers
1. C (Module 2.1)
2. C (Module 2.1)
3. B (Module 2.3)
4. A (Module 2.2)
5. D (Module 2.4)
6. A (Module 2.4)
7. D (Module 2.4)
8. A (Module 2.4)
9. A (Module 2.3)
10. C (Module 2.3)
11. C (Module 2.4)
12. A (Module 2.2)
13. B (Module 2.2)
14. D (Module 2.2)
15. B (Module 2.3)
16. C (Module 2.4)
17. A (Module 2.4)
18. A (Module 2.2)
19. D (Module 2.1)
20. C (Module 2.1)