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Certified Strength & Conditioning Specialist > Chapter 2: Biomechanics of Resistance Exercise > Flashcards

Chapter 2: Biomechanics of Resistance Exercise Flashcards

1
Q

Biomechanics

A

Study of the mechanisms through which musculoskeletal components interact to create movement

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2
Q

Origin

A

Proximal muscle attachment

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3
Q

Insertion

A

Distal muscle attachment

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4
Q

Proximal

A

Toward the center of the body

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5
Q

Distal

A

Away from the center of the body

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6
Q

Forms of Muscle Attachments

A
  • Fleshy attachments

- Fibrous attachments

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7
Q

Fleshy Attachments

A
  • Most often found at the proximal end of the muscle
  • Muscle fibers are directly affixed to the bone
  • Usually distributed over a wide area instead of focused on a single spot
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8
Q

Fibrous Attachments

A
  • Blend into and are continuous with muscle sheaths and connective tissue surrounding the bone
  • Ex: tendons
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9
Q

Tendons

A

A flexible but inelastic cord of strong fibrous collagen tissue attaching a muscle to a bone

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10
Q

Agonist

A
  • The muscle most directly involved in movement

- Prime mover

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11
Q

Antagonist

A

A muscle that can slow down or stop the movement

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12
Q

Synergist

A

A muscle that assists directly in a movement

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13
Q

Lever

A

A rigid/semi-rigid body that exerts a force on any object impeding its tendency to rotate

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14
Q

Fulcrum

A

The pivot point of a lever

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15
Q

Muscle Force

A

Force generated by muscle activity; tends to draw the opposite ends of a muscle toward each other

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16
Q

Resistive Force

A

Force generated by a source external to the body which acts contrary to muscle force

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17
Q

First-Class Lever

A
  • A lever for which the muscle force and resistive force act on opposite sides of the fulcrum
  • FAR
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18
Q

Second-Class Lever

A
  • A lever for which the muscle force and resistive force act on the same side of the fulcrum
  • FRA
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19
Q

Third-Class Lever

A
  • A lever for which the muscle force and resistive force act on the same side of the fulcrum
  • RFA
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20
Q

Mechanical Advantage

A
  • The ratio of the applied force and the resistive force
  • Mechanical advantage often changes continuously during human movement
  • MA > 1.0 → applied force can be less than the resistive force to produce an equal amount of torque
  • MA < 1.0 → applied force has to be greater than the resistive force to produce an equal amount of torque
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21
Q

Moment Arm

A
  • The perpendicular distance from the line of action of the force to the fulcrum
  • AKA force arm, lever arm, or torque arm
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22
Q

Torque

A
  • AKA moment;

- Force times the moment arm, causes a rotation

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23
Q

Why are muscle forces greater than the forces exerted by the body on objects?

A

Most muscles operate at a mechanical disadvantage

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24
Q

The trade-off in tendon insertion

A

The mechanical advantage gained by having tendons insert farther from the joint center is accompanied by a loss of maximum speed

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25
Q

What causes the tendon insertion trade-off?

A

When the tendon is farther from the joint center, the muscle has to contract more to make the joint move through a given range of motion

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26
Q

Anatomical Position

A

The body is erect, the arms are down at the sides, and the palms face forward

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27
Q

Sagittal Plane

A

Plane which divides the body into equal left-and-right portions

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28
Q

Frontal Plane

A

Plane which divides the body into equal front-and-back portions

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29
Q

Transverse Plane

A

Plane which divides the body into equal upper-lower portions

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30
Q

Sagittal Axis

A

Axis perpendicular to the frontal plane, about which all movements in the frontal plane occur

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31
Q

Frontal Axis

A

Axis perpendicular to the sagittal plane, about which all movements in the sagittal plane occur

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32
Q

Longitudinal Axis

A

Axis perpendicular to the transverse plane, about which all movements in the transverse plane occur

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33
Q

Strength

A

The ability to produce force

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34
Q

Force

A
  • A push or pull

- F = ma

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35
Q

Acceleration

A

Change in velocity over unit time

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36
Q

Work

A

W = force x distance

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37
Q

Power

A
  • Time rate of doing work

- Force x velocity

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38
Q

Force Conversion Factors

A
  • LBS x 4.448 = N
  • KG (mass ) x g = N
  • KG (force) x 9.807 = N
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39
Q

Distance Conversion Factors

A
  • FT x 0.3048 = m

- IN x 0.0254 = m

40
Q

Radians to Degrees Conversion Factor

A

DEGREES x 0.01745 = RADIANS

41
Q

Weight

A
  • F = mg

- g = acceleration due to gravity

42
Q

Positive Work/Power

A
  • Positive work: when the force exerted on a weight is in the same direction as the weight’s movement
  • Positive power: the rate at which positive work is done
43
Q

Negative Work/Power

A
  • Negative work: when the force exerted on a weight is in the opposite direction as the weight’s movement
  • Negative power: the rate at which negative work is done
  • Negative work actually refers to work done by the weight on the muscle
  • Weight lifted → muscle work increases weight’s potential energy
  • Weight lowered → weight work decreases weight’s potential energy
44
Q

Angular Displacement

A

The angle through which an object rotates

45
Q

Angular Velocity

A

The object’s rotational speed

46
Q

Rotational Work

A

Torque x angular displacement

47
Q

Rotational Power

A

Rotational work/time

48
Q

Strength vs Power

A

Strength is the capacity to exert force at any given velocity, and power is the mathematical product of force and velocity at whatever speed

49
Q

Biomechanical Factors in Human Strength

A
  • Neural Control
  • Muscle Cross-Sectional Area
  • Arrangement of muscle fibers
  • Muscle length
  • Joint angle
  • Muscle contraction velocity
  • Joint angular velocity
  • Strength-to-mass ratio
  • Body size
50
Q

Neural Control

A

Affects the maximal force output of a muscle by determining which and how many motor units are involved in a muscle contraction and the rate at which the motor units are fired

51
Q

Recruitment

A

How many motor units are involved in a muscle contraction

52
Q

Rate Coding

A

The rate at which the motor units are fired

53
Q

Neural Factors increasing force production

A
  • More motor units
  • Motor units are bigger
  • Faster firing rate
54
Q

Muscle Cross-Sectional Area

A

Greater cross-sectional area → greater strength (all other things equal)

55
Q

Arrangement of Muscle Fibers

A
  • Maximally contracting muscles have been found capable of generating forces of 23 to 145 psi
  • This wide range can be accounted for by the variation in fiber arrangement
56
Q

Pennate Muscle

A

Fibers align obliquely with the tendon

57
Q

Angle of Pennation

A
  • The angle between the muscle fibers and an imaginary line between the muscle’s origin and insertion
  • 0 = no pennation
58
Q

Radiate Pennation

A

Gluteus medius

59
Q

Longitudinal Pennation

A

Rectus abdominis

60
Q

Fusiform Pennation

A

Biceps brachii

61
Q

Multipennate

A

Deltoid

62
Q

Bipennate

A

Rectus femoris

63
Q

Unipennate

A

Tibialis posterior

64
Q

Pennation vs Nonpennation Strength and Velocity

A 
Greater pennation results in:
- More sarcomeres in parallel, rather than series
- Better able to generate force
- Lower max shortening velocity
Lesser pennation results in: 
- Higher contraction velocity
65
Q

Role of Muscle Length in Force Production

A

There’s an ideal amount of tension which maximally aligns actin and myosin, which allows for the greatest amount of force generation

66
Q

Muscle Contraction Velocity

A

Force capability decreases as velocity increases

67
Q

Concentric Muscle Action

A
  • Contraction → muscle shortens

- Torque capability decreases as angular velocity increases

68
Q

Eccentric Muscle Action

A
  • Contraction → muscle lengthens
  • Torque capability increases with angular velocity until ~90 degrees/second, then it declines
  • Greatest force capability is seen in eccentric muscle action
69
Q

Isometric Muscle Action

A

Contraction → muscle maintains length

70
Q

Strength-to-Mass Ratio

A

If mass is equal, the stronger athlete has an advantage

71
Q

Body Size

A
  • All other things being equal, a smaller athlete will be stronger pound-for-pound
  • As body size increases, mass increases faster than strength
72
Q

Classic Formula

A
  • Use to compare loads lifted between lifters
  • The load lifted is divided by body weight to the 2/3 power, accounting for the relationship of cross-sectional area vs volume
73
Q

Sources of Resistance to Muscle Contraction

A
  • Gravity
  • Inertia
  • Friction
  • Fluid Resistance
  • Elasticity
74
Q

“Advantages” of Stack Machines

A
  • Safety
  • Design flexibility
  • East of use
75
Q

Advantages of Free Weights

A
  • Whole-body training

- Simulation of real-life activities

76
Q

Inertial Force

A

Due to inertial forces, resistance is greater than bar weight in the beginning of a movement, less than at the end

77
Q

Bracketing Technique

A

The athlete performs the sport movement with less than normal and greater than normal resistance as a form of acceleration training

78
Q

Friction

A
  • The resistive force encountered when one attempts to move an object while it is pressed against another object
  • FR = k x FN
    FR = resistive force (friction)
    k = coefficient of friction
    FN = normal force
79
Q

Fluid Resistance

A
  • Resistive force encountered by an object moving through a fluid (liquid or gas), or by a fluid moving past or around an object or through an opening
  • Plays a large role in swimming, rowing, golf, sprinting, discus throwing, and baseball pitching
80
Q

Surface Drag

A

Results from the friction of a lfuid passing along the surface of an object

81
Q

Form Drag

A
  • Results from the way in which a fluid presses against the front or rear of an object passing through it
  • Cross-section area has a major effect on this type of drag
82
Q

Elasticity

A
  • Resistance provided by an elastic component is proportional to the distance it is stretched
  • Problem with elastic devices → muscles are stronger at beginning of ROM, elastic devices are most difficult at end ROM
  • FR = k * x
    FR = resistive force
    k = constant reflecting physical characteristics of elastic component
    x = distance stretched
83
Q

Back Injury and Resistance Training

A

85-90% of all disk herniations occur b/t L4 and L5

84
Q

Lordotic Spine

A
  • Lordotic lumbar spine refers to the curvature of the lower back, normally slightly arched
  • Lordotic lumbar spine is superior to rounded back for avoiding injury
85
Q

Kyphotic Spine

A

Kyphotic thoracic spine refers to the curvature of the upper back, normally slightly rounded

86
Q

Vertebral Column

A

Vertebral column has a natural S-curve

87
Q

Ventral

A

Toward the anterior

88
Q

Dorsal

A

Toward the posterior

89
Q

What is the fluid ball?

A

The abdominal fluids and tissue kept under pressure by tensing surrounding muscle (deep abdominal muscles and diaphragm)

90
Q

Valsalva Maneuver

A
  • Glottis is closed → Air cannot escape → abs and rib muscles contract → creates rigid components of liquid and air in torso and chest
  • Makes it easier to support heavy loads
91
Q

Effect of weight belts

A
  • Increase intra-abdominal pressure

- Belts are helpful, but should be used wisely

92
Q

What makes the shoulder joint so susceptible to injury?

A

Structures in the shoulder can easily impinge on one another, causing inflammation and degeneration of tissue

93
Q

Rotator Cuff Muscles

A
  • Supraspinatus
  • Infraspinatus
  • Subscapularis
  • Teres minor
94
Q

Knees and risk of injury

A
  • Rotary forces make the knee susceptible to injury

- Patella is most susceptible to injury from resistance training

95
Q

Knee Wraps

A

Only use knee wraps if absolutely necessary, and only then on the heaviest sets

96
Q

Primary Concerns for the Elbow and Wrists

A

Most common source of injury is throwing style movements

Certified Strength & Conditioning Specialist (24 decks)

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