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APA2315-Intro to Applied Biomechanics > Quiz 4 > Flashcards

Quiz 4 Flashcards

1
Q

What are 4 things that coaches, athletic therapists and teachers do?

A
  1. Develop new training techniques
  2. Minimize the risk of injury
  3. Establish the best rehabilitation treatment in case of injury
  4. Monitor the athlete’s full recovery
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2
Q

What are the 7 movement principles?

A

Balance
Inertia
Coordination continuum
Range of motion
Segmental interaction
Force-motion
Force-time

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3
Q

What are the 2 projectile principles?

A

Optimal projection
Spin

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4
Q

What are the 3 relationships in muscle mechanics?

A

Force–Velocity Relationship,
Force–Length Relationship,
Force–Time Relationship

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5
Q

What are the 4 training principles?

A

Specificity
Overload
Adaption/Recovery
Recovery / detraining

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6
Q

What are 2 forms of displacement?

What are 3 forms of constant velocity?

What are 2 forms of constant acceleration?

A

vector vs scalar

Constant velocity:
walking
jogging
swimming
(sf = si + vi∆t)

Uniform acceleration:
gravity
friction
(vf = vi + a∆t; sf = si + vi∆t + ½a∆t2 ;
vf2 = vi2 +2a∆d; sf = si + ½(vi + vf) ∆t )

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7
Q

What is the formula for the relation between linear and angular kinematics?

A

Linear – angular kinematics: (s=r(theta))

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8
Q

What one thing is the motion of a body influenced by and in what direction?

What is the only type of acceleration that the body experiences and in what direction?

How much is acceleration horizontally?

A

The motion of a body is influenced only by gravity (in the vertical direction).

Therefore the ONLY acceleration that the body experiences is a vertical acceleration due to gravity of 9.81 m/s2 in the DOWNWARD direction

Horizontally, acceleration must be zero, since no forces act in this direction(ignore air resistance)

Equation for constant horizontal motion applies
– Where sfx and six are the final and initial displacements in the xdirection and
– vix is the initial and constant velocity in the x direction
– t is the time component

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9
Q

What are Newton’s 3 laws?

A

Newton Laws:

Law of Inertia: all objects have the inherent property to resist a change in their state of motion.

Law of Momentum or Law of Acceleration:
(F = ma) .

Law of Reaction: for every action there is an equal and opposite reaction.

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10
Q

What are the 4 types of dynamics?

A

Dynamics:

Force(N)
Inverse Dynamics(m/s2)
Momentum(p)(kg.m/s)
Impulse (J)(N.s)

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11
Q

What is the formula for force and what is the unit of measurement?

A

Force:

mass x acceleration (f = m x a)

N

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12
Q

What is the formula for inverse dynamics and what is the unit of measurement?

A

Inverse Dynamics:

acceleration = force/mass (a = f/m)

m/s2

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13
Q

What is the formula for momentum and what is the unit of measurement?

A

Momentum(p):

momentum = mass x velocity (p = m x v)

kg.m/s

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14
Q

What is the formula for impulse and what is the unit of measurement?

A

Impulse(J):

force x time (J = ∑F x Δt)

N.s

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15
Q

What does angular motion occur about?

What are the 3 types of axis for angular motion?

A

Occurs about an axis

  1. Mediolateral axis (Sagittal plane):
    divides the body into left and right halves
  2. Anteroposterior axis (Frontal plane):
    divides the body into front and back halves
  3. Vertical axis (Transverse plane):
    divides the body into top and bottom halves
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16
Q

What are the 3 types of energy and what is the formula?

A

Energy:
Potential energy
Kinetic energy linear
Kinetic energy rotational

(E = mgy + ½ mvx2 + ½ mvy2 + ½ Icgω2)

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17
Q

What are the 2 different types of work and what is the formula?

A

Work:
Positive work
Negative work

W =∆E =change in mechanical energy=Ef –Ei)
W = (mgyf + ½ mvx2f + ½ mvy2f + ½ Icgω2f) – (mgyi + ½ mvx2i + ½ mvy2i+ ½ Icgω2i)

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18
Q

What is the unit for power?

What is the formula for average power and instantaneous power?

A

Watts

Average power (Watts):
Work/time (Joules/sec)

Instantaneous power:
P = ∆E/∆ t (W)

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19
Q

What are the 3 types of drag?

A

Three types of drag:
1) form drag (pressure difference between the front and back of the swimmer) pressure

2) wave drag (the resistance of a wave) “pushing water”

3) surface drag (body surface and water molecules)“friction”

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20
Q

What is bernoulli’s principle?

A

Bernoulli’s principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid’s potential energy.

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21
Q

What causes the magnus effect?

What are 3 examples of the magnus effect?

A

-possibly due to bernoulli principle or turbulent flow around roughly surfaced object
-roughness can be caused by laces (baseball), dimples (golf ball), wear (table tennis) or nap (lawn tennis)

Magnus effect
* Distance
* Golf
* Curve ball
* Soccer

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22
Q

How do lift and drag relate?

A

Angle of attack changes relationship between lift and drag

Too steep creates excessive drag
Not steep enough reduces lift

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23
Q

What is bernoulli’s principle about lift?

A

lift force on an air foil may be explained by bernoulli’s principle

higher air flow on top of wing reduces pressure producing a lift force (Bernoulli)

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24
Q

What are the 7 training principles for the 7 movement principles?

A

Range of motion:
Increase the range of movement to improve force applied and coordination (stability)

Segmental interaction:
Isolate active muscle groups (limbs)

Coordination:
Loading curves, transfer of momentum between segments

Force - motion:
Eccentric-concentric-isometric: force curve for muscle groups

Force - time:
Muscle contraction fast vs. slow twitch.

Inertia:
Loading of muscle groups (plyometric) (push –pull)

balance:
Strong and stable base

spin:
N/A

Optimal projection:
N/A

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25
Q

What are 4 ways to use specificity in training?

A

Specificity
1. Range of motion, isolate the limb(s)
2. Strength
3. Speed of contraction
4. Type of contraction

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26
Q

What are 3 ways to use overload in training?

A

Overload
1. Increasing resistance
2. Increasing reps
3. Increasing load of range of motion

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27
Q

What are 2 ways to use adaptation/recovery in training?

A

Adaptation/Recovery
1. Energy systems
2. hypertrophy

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28
Q

What is the fourth principle of training after specificity, overload and adaptation/recovery?

A

Recovery/Detraining

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29
Q

What are 7 ways to train for the slapshot?

A

Shoulder and arm strength with pullups

Shoulder and core strength with renegade rows

Shoulder-trunk range of motion and balance “force-time” with med ball rotational throws

Wrist-arm-core-shoulder endurance with battle ropes

Shoulder and core strength (speed) with banded rows

Shoulders and core speed and flexibility with russian twists

Force-distance with banded slap shots

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30
Q

What are the 4 types of movement that produce motion in humans?

A

Movements that produces locomotion/gait for humans:
– walking
– running
– swimming
– cycling

31
Q

What are 3 characteristics of gait?

A

Characteristics:
– energy-economical, particularly walking

– Robust systems, flexibility to cope with different speeds, terrains, injuries etc.

– sophisticated control mechanisms (bipedal gait inherently unstable)

32
Q

Wat is the definition of a stride?

What is the definition of a step?

How many strides are in a step?

What are 3 properties of a stride/step?

A
  • Stride: a complete gait cycle, measured from one heel strike to next heel strike of the same foot
  • Step (= pace): interval from heel strike of one foot tosubsequent heel strike of the other foot
  • Therefore: 1 stride = 2 steps
  • The terms “stride” and “step/pace” may refer to any of the following properties of the relevant movement:
  • time duration
  • distance covered
  • number
33
Q

What are the 2 phases of gait in walking?

What are the 2 support phases in walking?

A

Stance phase and swing phase

*Alternating periods of double and single support
*About 70:30 split between single and double support in normal walking

34
Q

What is the definition of cadence?

What is the definition of cycle time?

What is the average cadence, cycle time (s), stride length (m), and speed (m/s) for young adult males?

Is natural gait optimal?

Are walking speeds higher in towns or rural environments?

A

Cadence: steps taken per minute

Cycle time(stride time) : stride duration in seconds

Cadence = 90-135 steps/minute
cycle time = 0.9-1.3 seconds
stride length = 1.2-1.8 metres
speed = 1.1-1.8 m/s

  • Natural walking speeds, and stride lengths, are close to the optimum for energy efficiency
  • Walking speeds higher in towns than in rural environments
35
Q

What are the 3 principal forces?

Which 2 of these forces are external?

What are 2 situations in which muscle force was examined?

A

The principal forces are:
– body weight (BW)
– ground reaction force (GRF)
– muscle force (MF)

BW and GRF are external forces; so the movement of the centre of mass (CoM) can be predicted from them alone.

MF must be examined however if we wish to
consider either of the following:
– movements of individual limbs or body segments
– why GRF changes in magnitude and direction during the gait cycle.

36
Q

do muscle forces influence body movement directly or indirectly?

A

Muscle forces can only influence the movement of the body as a whole indirectly, by their effectson the GRF

37
Q

What are 4 key characteristics of the gait mechanism?

A

1.Walking is a precise, co-ordinated set of movements involving multiple joints and body segments

  1. It comprises a pattern of alternating action of the two lower limbs
  2. Pendulum-like movements of the limbs give rise to two distinct phases: swing and support (or stance)
  3. In walking, but not running, the support phases of the two legs overlap
38
Q

What are the 4 forces involved in walking?

A
  • When starting to move, we lean forward (MF)
  • As the body starts to fall (BW), a leg is extended forwards and halts the fall (MF; GRF)
  • At the same time, the other leg “kicks off, upwards and forwards” (MF; GRF) in order to keep the body moving forwards.
  • This forward momentum carries the body forward into the next forward fall, i.e. the start of the next step
39
Q

In which direction does body weight act?

In what situation does it produce torque?

What does torque cause?

What does bodyweight contribute to?

A
  • Always acts vertically downwards from the Centre of Mass
  • If its line of action does not pass through a joint, it will produce a torque about that joint
  • The torque will cause rotation at the joint unless it is opposed by another force (e.g. muscle, or ligament)
  • BW contributes to GRF (ground reaction force)
40
Q

What are the 2 types of force within ground reaction force?

A

“Action” force
* Push exerted on ground by foot
* Results from the sum of the following Body weight + impact force of foot on ground (at footstrike only) + “pushing force” from contraction of extensor muscles (towards end of stance phase)

“Reaction” force
* Push exerted by ground on foot, as a consequence of Newton’s 3rd Law.
* Equal magnitude, opposite direction, same point of application as action force.
* If line of the reaction force does not pass through a joint, it will produce a torque about that joint

41
Q

What does muscle activation generate in human movement and what does this do?

What 2 types of muscle activity are present in gait?

A

In gait, as in all human movement, muscle activation generates internal joint moments (torques) that:
– Contribute to ground reaction force
– Ensure balance
– Increase energy economy
– Allow flexible gait patterns
– Slow down and/or prevent limb movements

Much muscle activity during gait is eccentric or isometric, rather than concentric

42
Q

What is the butterfly diagram relating to ground reaction force?

A

There is a peak at the left side representing the heel and then it dips down when the whole foot is on the ground and then there is another peak at the right side representing the toe

43
Q

What are the 3 ways that ground reaction force varies through the stance phase?

A

GRF varies, through the stance phase, in terms of all three aspects namely:
– Magnitude
– Direction
– Point of action (= centre of pressure)

44
Q

What are 2 ways we can separate ground reaction forces?

A

Separate them horizontally and vertically

45
Q

What does the direction of the horizontal component tell us about ground reaction force?

A

The direction of the horizontal component (i.e.
forwards or backwards) tells us whether the body is
accelerating or decelerating in its forwards movement
at that moment of time

46
Q

What does the magnitude of the vertical component tell us about ground reaction force?

A

The magnitude of the vertical component (and
specifically whether it is greater or less than body
weight) tells us what is happening to the vertical
movement of the body

47
Q

What is the difference between how GRF acts initally and then how GRF acts at the end?

A

Initially GRF acts diagonally backwards and upwards, from the heel.
The horizontal component acts backwards, and the vertical component is greater than that of body weight. GRF at this moment therefore:
– stops the “controlled downwards fall” of the body
– exerts a braking, or slowing, effect on forward movement
* During the middle of the stance phase the GRF:
– remains > body weight and therefore the CoM is lifted up slightly in midstance.
– point of action moves forward from the heel.
– line of action becomes more nearly vertical and therefore the
braking/slowing effect disappears
* After the midpoint of the stance phase the vertical component of GRF falls (< body weight) as the leg passes the vertical position and the CoM moves downwards.
* At the end of the stance phase, the GRF increases in magnitude again, acting forwards and upwards. This gives the necessary propulsive force to stop downwards movement of the CoM, and to to keep the body moving forwards.

48
Q

How does the center of pressure change throughout a step?

A

CoP is initially near the lateral edge of the heel

  • As the stance (support) phase progresses, it moves forwards
    and medially, ending up under the big toe.

Note: balance is primarily managed under the “ball” of the foot.

49
Q

How energy efficient is walking?

What are the 2 types of mechanical energy involved in walking?

A

Walking is very energy-efficient: little ATP is required.
* This is because of various mechanisms that ensure the
mechanical energy the body has is passed on from one step to the next.

The two forms of mechanical energy involved are:
*kinetic energy (energy due to movement
*potential energy (energy due to position)

50
Q

What type of motion does walking relate to?

A
  • A pendulum is an object, swinging from a fulcrum,
    under the influence of gravity.
  • A pendulum has a natural frequency of swing that is
    dependent on its mass, and the distance from the
    fulcrum to its CoM.
  • During the swing of a pendulum, potential and kinetic
    energy are interconverted and therefore, overall,
    energy is conserved.
  • Both the upper and lower limbs of the human body can
    move with pendulum motion, with or without muscle
    assistance.
51
Q

How do potential energy and kinetic energy change in a pendulum?

A

Three points on a pendulum swing are illustrated.

As the pendulum swings away from the midpoint, in either direction, KE is progressively converted into PE

At the extreme points in the swing, there is no KE at all and all the energy is present as PE

52
Q

What are the stages of pendulum action during a swing phase?

A
  • The legs move as conventional pendulums during the swing
    phase (with a little assistance from the hip flexors).
  • This reduces the amount of muscle energy needed to move the swinging leg forward
  • It also accounts for the “natural” frequency of gait that has
    optimal energy efficiency (see slide 7)
  • Although the legs swing forwards much like pendulums, they are prevented from swinging backwards by foot strike.
  • During the stance phase, the leg can be viewed as an “inverted pendulum”. This action also involves inter-conversion of potential and kinetic energy
53
Q

What is an inverted pendulum and which phase of gait does energy act in an inverted pendulum?

A

The pendulum “bounces” backwards and forwards, using the springs.

high PE/low KE at the top and low PE/high KE on the sides

Stance phase

54
Q

What are the stages of action during a stance phase?

A

During the stance phase, the leg can be viewed as an “inverted pendulum”.

  • The forward momentum of the body gives it the necessary initial angular velocity of rotation (taking the place of the “spring” on the previous slide).
  • “Inverted” pendulum action also involves inter-conversion of potential and kinetic energy, but in this case (unlike a conventional pendulum) KE reaches a minimum at the midpoint of the motion, and PE is highest at that point.
  • When reaching the endpoint of its “inverted swing” the stance leg does not swing back, as a real inverted pendulum would, because the foot is taken off the floor, the fulcrum transfers from the foot to the hip, and the leg swings again as a conventional pendulum.
55
Q

How does the rolling lemon model relate to walking?

A

Pendulum considerations help us understand energy efficiency by concentrating on the individual legs.

Ultimately, we need to consider the energy of the
whole body

A simple model that allows this is that of a rolling ellipse, with the midpoint of the ellipse representing the CoM of the body

At the midstance point for either leg, the CoM of the whole body is relatively high (despite the best efforts of the Determinants of Gait). Therefore PE for the whole body is relatively high, and KE (forwards movement velocity )
relatively low.

56
Q

What are the qualitative and quantitative differences between running and walking?

A

The main qualitative difference between walking and
running is the flight phase (i.e. period of no support)
and the absence of a period of double support.

  • An important quantitative difference is that, in running
    gait, the foot hits the ground less far in front of the
    body’s centre of gravity, compared with walking (i.e.
    when we run, the forward swinging leg “sticks out”
    less far in front of the trunk at footstrike).
  • This characteristic is more pronounced the faster the
    run.
57
Q

What are the consequences caused by the differences between running and walking?

A

When running, the body’s momentum alone has to carry
it over the support foot, as the other foot is not in contact
with the ground.

  • The position of heel strike, relative to the CoM, helps with
    this (see previous slide), because it means that the CoM
    is not lowered as much at foot strike.
  • The position of heel strike relative to the CoM also
    reduces the ‘braking effect’ of the GRF during the first
    part of the stance phase
58
Q

What are 2 key things that happen during the transition from walking to running?

A

During transition from walking to running:

*the period of double support disappears
*a greater proportion of the pace time is spent in the
swing phase:

59
Q

How are stride rate and length changed during running?

A

As running speed increases, both stride rate and length
become higher.

  • Initially, at relatively low speeds, the changes are
    proportionally greater in length than in rate
  • Near maximum speed, however, rate increases more
    than length.
  • The explanation for this is in terms of energy efficiency
  • In energy terms, it is more efficient to increase speed by
    taking longer paces rather than taking them more rapidly
60
Q

How is the GRf butterly different between running and walking?

A

Compared with walking:
* Initial ‘contact’ peak is smaller and is not angled back
as far (less braking effect)
* Final ‘thrust’ peak is larger (need to project body into
flight phase, faster speeds etc)
* Duration of contact phase is shorter – of course!

Mainly a smaller heel speak and a bigger toe peak

61
Q

What are special energy considerations when running?

A

Energy usage differs fundamentally between running
and walking
* In running, both kinetic and potential energy are high
during the flight phase.
* Energy storage in elastic tissues at the start of the
support phase has a more prominent role in running.
* By contrast, elastic energy storage during walking
is smaller – in fact we ignored it altogether

62
Q

What type of model is used for running as compared to the rolling lemon model with walking?

What are the 3 different forms of energy used for running?

A

Contrast this with the rolling lemon model for walking.

Here, KE and PE are both high at the top of the “bounces” (equivalent to the middle of the flight phase)

During ground contact, KE and PE are lower, and energy is stored in elastic tissues.

So, for running, we have to consider interconversion between three different forms of energy: PE, KE and elastic

63
Q

How is elastic energy storage used during running?

A

Total kinetic energy dissipation at footstrike= 100 J/pace (70 kg subject; 4.5. m s-1)

  • At start of support phase, elastic energy (from the foot impact) is stored in:
    – Achilles tendon ~35J
    – Patellar tendon ~20J
    – Arch of foot ~17J
    TOTAL ~72J
  • Thus, almost ¾ of the kinetic energy that would otherwise be lost at foot strike, is instead stored as elastic energy, in ligaments and tendons, and recovered in kinetic form during the latter parts of the support phase
  • Due to this elastic energy storage, muscles do not need to
    contract as far or as fast, and metabolic energy use, in the form of ATP, is reduced
64
Q

What are the two mechanisms that affect the amount of force a muscle can produce through its range of motion?

A

There are two principles that govern the relationship between motor neuron activity and muscle force: the rate code and the size principle.

65
Q

What are the difference between stabilizing and destabilizing forces at a joint in a curl?

A

stabilizing forces run parallel to the forearm and destabilizing forces run perpendicular to the forearm

66
Q

What is the length-tension relationship within a muscle?

A

As the muscle length increases, the active tension in the muscle rises to a peak and then lowers like a parabola and the passive tension increases but the total tension increases

Passive force is defined as the increase in passive, steady-state, isometric force of an actively stretched muscle compared with the same muscle stretched passively to that same length.

Active force is defined as the rise in force observed on activation of a muscle and is associated with cross-bridge interactions between myosin and actin.

67
Q

Describe how the muscle cell converts chemical energy into
mechanical energy?

A

During muscle contraction, chemical energy is converted to mechanical energy when ATP is hydrolysed during cross-bridge cycling. This mechanical energy is then distributed and stored in the tissue as the muscle deforms or is used to perform external work.

68
Q

How does the overlap of the actin and myosin fibres effect the
amount of force a muscle can produce?

A

Cross-bridges can only form where thick and thin filaments overlap, allowing myosin to bind to actin. If more cross-bridges are formed, more myosin will pull on actin and more tension will be produced. Maximal tension occurs when thick and thin filaments overlap to the greatest degree within a sarcomere.

69
Q

Describe the relationship between muscle force and contraction velocity as based on the force velocity curve

A

From most force to most velocity:

maximal strength
strength-speed
power
speed-strength
speed

70
Q

Describe the relationship between load and shortening velocity for eccentric contraction and concentric contraction

A

Force is highest during the eccentric or lengthening phase and goes down, velocity is 0 during the isometric phase and the force continues to go down to it’s lowest point during the concentric or shortening phase

continous downward curve

71
Q

Does peak power of a muscle contraction occur at high velocity, low velocity or in the middle at average velocity and why?

A

Peak power occerus at an average velocity or the middle of the curve

72
Q

What are the shapes of the passive and active force-length curves?

A

passive force has a exponential upward curve which exponentially increases as muscle length occurs

active force has a downward parabolic curve which has a peak when the crossbridges are at optimal overlap and then both sides are when they’re too far or too close

73
Q

What is the best hockey movie of all time?

A

Slapshot

APA2315-Intro to Applied Biomechanics (4 decks)

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