Chapter 2: Biomechanics of Resistance Exercise Flashcards
(211 cards)
1
Q
What is the study of the mechanisms through which the musculoskeletal components interact to create movement?
A
Biomechanics
2
Q
List 5 primary sources of resistance to muscle contraction used in exercise devices.
A
GIFFE (Gosh I Feel Fantastic Everyday)
- gravity
- inertia
- friction
- fluid resistance
- elasticity
3
Q
Term for ‘toward the center of the body.’
A
proximal
4
Q
Term for ‘away from the center of the body.’
A
distal
5
Q
Fill in the blank:
The muscle’s __________ is its proximal attachment to the bone.
A
origin
6
Q
Fill in the blank:
The muscle’s __________ is its distal attachment to the bone.
A
insertion
7
Q
What kind of muscle attachments are most often found at the proximal end of a muscle with the muscle fibers directly affixed to the bone, usually over a wide area so that force is distributed rather than localized?
A
fleshy attachments
8
Q
Fill in the blank:
Fibrous muscle attachment, such as _______, blend into and are continuous with both the muscle sheaths and the connective tissue surrounding the bone.
A
tendons
9
Q
True or False:
Tendons have additional fibers that extend into the bone itself, making for a very strong union.
A
True
10
Q
Define agonist.
A
The muscle most directly involved in bring about a movement.
11
Q
Fill in the blank:
The muscle that can slow down or stop the movement is called the ___________.
A
antagonist
12
Q
True or False:
The antagonist assists in joint stabilization and in braking the limb toward the end of a fast movement.
A
True
13
Q
Multiple choice:
During throwing, the triceps acts as an a)___________, extending the elbow to accelerate the ball. As the elbow approaches full extension, the biceps acts as an b)_____________ to slow down elbow extension and bring it to stop, thereby protecting elbow structures from internal impact.
A
a) agonist
b) antagonist
14
Q
Define synergist.
A
A muscle that assists indirectly in a movement.
15
Q
Fill in the blank:
Muscles that stabilize the scapula act as _________ during upper arm movement.
A
synergists
16
Q
True or False:
Synergists are not required to control motion when the agonist is a muscle that crosses two joints.
A
False
17
Q
A lever for which the muscle force and resistive force act on opposite sides of the fulcrum.
A
first-class lever
18
Q
The pivot point of a lever.
A
fulcrum
19
Q
A rigid or semirigid body that, when subjected to a force whose line of action does not pass through its pivot point, exerts force on any object impeding its tendency to rotate.
A
lever
20
Q
The ratio of the moment arm through which an applied force acts to that through which a resistive force acts.
A
mechanical advantage
21
Q
Define first-class lever.
A
A lever for which the muscle force and resistive force act on opposite sides of the fulcrum.
M-F-R
MUSCLE - FULCRUM -RESISTANCE
22
Q
Define fulcrum.
A
The pivot point of a lever.
23
Q
Define lever.
A
A rigid or semirigid body that, when subjected to a force whose line of action does not pass through its pivot point, exerts force on any object impeding its tendency to rotate.
24
Q
Define mechanical advantage
A
The ration of the moment arm through which an applied force acts to that through which a resistive force acts.
25
# Fill in the blank: greater or lesser
A mechanical advantage, represented as a ratio ______ than 1.0 allows the applied (muscle) force to be less than the resistive force to produce an equal amount of torque.
greater
The muscle doesn't have to work as hard to produce an equal amount of torque against the resistive force (like a dumbbell.)
26
# Fill in the blank: more or less
A mechanical advantage of a ratio ______ than 1.0 indicates that one must apply greater (muscle) force than the amount of resistive force present.
less
If the resistive force (ie. dumbbell) makes the muscle work harder then this would be a disadvantage for the muscle.
27
The perpendicular distance from the line of action of the force to the fulcrum.
moment arm
28
Define moment arm.
The perpendicular distance from the line of action of the force (applied or resistive) to the fulcrum.
29
Force arm, lever arm and torque arm is just another way of describe what type of arm?
moment arm
30
Force generated by biomechanical activity, or the stretching of noncontractile tissue, that tends to draw the opposite ends of a muscle toward each other.
muscle force
31
Force generated by a source external to the body (eg. gravity, inertia, friction) that acts contrary to muscle force.
resistive force
32
Define second-class lever.
A lever for which the muscle force and resistive force act on the same side of the fulcrum, with the muscle force acting through a moment arm longer than that through which the resistive force acts.
Moment arm of the muscle force is longer than moment arm of the resistive force while both are on the same side of the fulcrum.
F-R-M
FULCRUM-RESISTANCE-MUSCLE
or
M-R-F
MUSCLE-RESISTANCE-FULCRUM
(resistance is closer to the word fulcrum than muscle meaning it's moment arm is shorter)
33
An example of a second-class lever.
Heel raise. When the calf muscles work to raise the body onto the balls of the feet.
The required muscle force (calf) is smaller than the resistive force (body weight).
34
An example of a first-class lever.
Elbow extension against resistance (e.g. a triceps extension exercise).
M-F-R
MUSCLE-FULCRUM-RESISTANCE
triceps - elbow joint - dumbbell
35
A lever for which the muscle force and resistive force act on the same side of the fulcrum with the muscle acting through a moment arm longer than that through which the resistive force acts.
second-class lever
F-R-M
FULCRUM-RESISTANCE-MUSCLE
which ever force is closer to the word 'fulcrum' that is the shorter moment arm
36
Define third-class lever.
A lever for which the muscle force and resistive force act on the same side of the fulcrum, with the muscle force acting through a moment arm shorter than that through which the resistive force acts.
F-M-R
FULCRUM-MUSCLE-RESISTANCE
The muscle force is closer to the fulcrum or pivot point than the resistive force.
37
# Fill in the blanks: greater or lesser
The mechanical advantage in a third-class lever is a)________ than 1.0 so the muscle force has to be b)_________ than the resistive force to produce torque equal to that produced by the resistive force.
a) lesser
b) greater
```
Third class lever
F-M-R
```
38
What is the degree to which a force tends to rotate an object about a specified fulcrum?
torque
39
Define torque.
The degree to which a force tends to rotate an object about a specified fulcrum.
40
# Fill in the blank:
The magnitude of a force times the length of its moment arm is called __________.
torque
41
The moment arm of the muscle force divided by the moment arm of the resistive force gives you the ___________.
mechanical advantage
42
True or False:
Most human muscles that rotate the limbs about body joints operate at a mechanical advantage of ________ than 1.0.
less
Most human muscles work at a mechanical disadvantage.
43
A bicep curl is an example of what kind of lever?
Third-class lever
F-M-R
FULCRUM-MUSCLE-RESISTANCE
elbow joint - biceps - dumbbell
44
Triceps extension with resistance is an example of what kind of lever?
First-class lever
M-F-R
MUSCLE-FULCRUM-RESISTANCE
triceps - elbow joint - dumbbell
45
True or False:
Internal muscle forces are much greater than the forces exerted by the body on external objects because the muscles operate at a mechanical disadvantage most of the time.
True
46
True or False:
In knee extension and flexion, the location of the axis of rotation does not change throughout the range of motion.
False
Mechanical advantage often changes continuously during real-world activities. In the case of the knee, as it is not a true hinge joint, the location of the axis of rotation changes throughout the range of motion affecting the length of the moment arm through which the quadriceps and hamstrings act. Fro knee extension, the patella, or kneecap, helps to prevent large changes in the mechanical advantage of the quadriceps muscle by keeping the quads tendon from falling in close to the axis of rotation.
47
How does mechanical advantage change during resistance training with free weights?
The moment arm through which the weight acts equals the horizontal distance from a line through the center of mass of the barbell to the body joint about which rotation of the limb occurs; the resistive moment arm thus varies throughout the movement.
For example: a biceps curl. The fulcrum is the elbow. When the elbow is full extended with the weight in hand, the horizontal distance from the center of the weight to the elbow joint is very short (the weight is directly beneath the elbow joint). But when the curl is halfway up making a 90° angle at the elbow, the moment arm of the resistive force is at it's longest (the length of the elbow to the center of the weight). Thus, there is more mechanical advantage for the biceps with elbow fully extended and less mechanical advantage for the biceps (biceps work their hardest) at the halfway point of the curl.
48
# Fill in the blank: advantage or disadvantage
Most of the skeletal muscles operate at a mechanical _____________ due to the lever arrangement within the body and relative to the external forces the body resists.
disadvantage
49
# Fill in the blanks:
A person whose tendons are inserted on the bone farther from the joint center should be able to lift a)__________ weights because muscle forces acts through a b)_________ moment arm and thus can produce greater c)_________ around the joint.
a) heavier
b) longer
c) torque
50
# Fill in the blank: higher or lower
During sport and other physical activities, forces in the muscles and tendons are much ___________ than those exerted by the hands or feet on external objects or the ground.
higher
51
True or False:
The points at which tendons are attached to bone vary from person to person.
True
52
# Fill in the blank:
The tradeoff of having tendons insert farther from the joint center is that though there is greater mechanical advantage for the muscle there is a loss of maximum ________ because the muscle has to contract more to make the joint move through a given range of motion.
speed
53
# Fill in the blank: 'farther from' or 'closer to'
In slower movements like powerlifting, tendon insertion a)_________ the joint can be advantageous. While higher speed activities like tennis, the tendon insertion being b)___________ the joint would be advantageous.
a) farther from
| b) closer to
54
List the 3 planes of the human body in the anatomical position.
1. sagittal
2. frontal (or coronal)
3. transverse
55
Describe anatomical position.
The body is erect, the arms are down at the sides, and the palms face forward.
56
Define strength.
Strength is the ability to exert force.
57
Define acceleration.
Change in velocity per unit of time.
58
The ability to exert force.
Strength
59
Change in velocity per unit of time.
Acceleration
60
What is Newton's second law?
Force = Mass x Acceleration
FMA
61
What is the measurement of the ability to exert force at higher speeds?
Power
62
# Fill in the blank:
The time rate of doing work is know as _________.
Power
63
Define work.
Work is the product of the force exerted on an object and the distance the object moves in the direction in which the force is exerted.
64
Quantitatively, how is work defined?
Work = Force x Displacement
WFD
What F%*k Dude!
65
Quantitatively, how is power defined?
Power = Work/ Time
PWT
Paint With This
66
Force is measured in _________.
newtons (N)
67
Distance is measured in __________.
meters (M)
68
Work is measured in ___________.
joules (J or newton-meters or N•m)
69
Time is measured in __________.
seconds (s)
70
Power is measured in ___________.
watts (W, or J/s)
71
What equals the product of force and velocity?
Power
72
# Fill in the blank:
When force is exerted on a weight in the direction opposite to the one in which the weight is moving (as when a weight is lowered in a controlled manner), calculated power has a __________ sign.
negative
73
# Fill in the blank:
"Negative" power and work occur during ___________ muscle actions, such as lowering a weight or decelerating at the end of a rapid movement.
eccentric
74
What is "negative" work?
When force is exerted on a weight in the direction opposite to the one in which the weight is moving (as when a weight is lowered in a controlled manner). The muscular actions in negative work are eccentric.
75
True or False:
Negative work really refers to work performed on, rather than by, a muscle.
True
76
# Fill in the blank: lowered or lifted
When a weight is __________ muscles perform work on the weight, increasing the weight's potential energy.
lifted
77
# Fill in the blank: lowered or lifted
When a weight is ____________, its potential energy is used to perform an equal amount of work on the muscle.
lowered
78
True or False:
While repetitions of lifting and lowering a weight are performed, the athlete and weight alternately perform work on each other, rather than the athlete's alternately performing positive and negative work.
True
79
# Fill in the blank:
The rate at which weight lifting repetitions are performed determines the ___________.
power output
80
The angle through which an object rotates is called its ______________.
angular displacement
81
What is the SI unit for angular displacement?
the radian (rad)
82
1 rad = ?
180° ÷ π = 57.3°
83
What is the term for an object's rotational speed, measured in radians per second (rad/s)?
angular velocity
84
What is the equation for rotational work?
(Rotational) Work = Torque • Angular Displacement
WTA
85
True or False:
Power is a direct mathematical function of force and work.
False
Power is a direct mathematical function of force and velocity.
86
True or False:
Although the word strength is often associated with slow speeds and the word power with high velocities of movement, both variable reflect the ability to exert force at a given velocity.
True
87
True or False:
Powerlifting involves higher mechanical power than Olympic lifting.
False
Powerlifting is misnamed. Olympic lifting involves higher mechanical power.
88
# Fill in the blanks:
For a sport movement made relatively slow by high resistance, a)___________ strength is critical, whereas for a movement that is very fast due to low resistance, b)__________ strength is important.
a) low-velocity
| b) high-velocity
89
High-velocity strength or low-velocity strength.
What type of strength would an American football lineman need?
low-velocity strength
Their velocity of movement is slowed by the muscular force exerted by the opposing player as well as the inertia of the opposing player's body mass. Because the muscles are prevented from contracting at high velocity, the ability to exert force and power at low velocity is important.
90
High-velocity strength or low-velocity strength.
What type of strength would a badminton player need?
high-velocity strength
The badminton player's muscles quickly reach high velocity as a result of the minimal inertial resistance of the lightweight racket and the player's arm. Therefore, the ability to exert force and power at high velocity is critical to making rapid adjustments in a stroke.
91
True or False:
The sport of weightlifting (Olympic lifting) has a much higher power component than the sport of powerlifting, due to the higher movement velocities with heavy weights of the weightlifting movements.
True
92
What are the biomechanical factors involved in the manifestation of human strength? Name 9 factors.
1. neural control
2. muscle cross-sectional area
3. arrangement of muscle fibers
4. muscle length
5. joint angle
6. muscle contraction velocity
7. joint angular velocity
8. strength to mass ratio
9. body size
NMAMJMJSB
93
Which biomechanical factor affects the maximal force output by determining which and how many motor units are involved in a muscle contraction and the rate at which the motor units are fired?
neural control
94
Define recruitment.
The number of motor units involved in a muscle contraction.
95
Define rate coding.
The rate at which motor units are fired.
96
The number of motor units involved in a muscle contraction is called ___________.
recruitment
97
The rate at which motor units are fired is called _________.
rate coding
98
Muscle force is greater when:
I. more motor units are involved in a contraction
II. the motor units are greater in size
III. the rate of firing is faster
a. I & II only
b. II & III only
c. I & III only
d. I, II, & III
d
99
Much of the improvement in strength evidenced in the first few weeks of resistance training is attributable to what?
neural adaptations as the brain learns how to generate more force from a given amount of contractile tissue.
100
True or False:
Muscle hypertrophy is, initially, a faster mechanism for improvement in strength than neural adaptations of the brain.
False
101
True or False:
All else being equal, the force a muscle can exert is related to its cross-sectional area rather than to its volume.
True
102
# Fill in the blank:
Resistance training increases both the strength and _________ of muscle.
cross-sectional area
103
Two athletes of similar body fat but different height have the same biceps circumference. The taller and heavier athlete has longer biceps and therefore more volume of bicep muscle than the shorter athlete. Which athlete has stronger biceps? The taller or shorter one?
Both have the same biceps strength as strength is about the cross-sectional area of the muscle and not about the volume. Since both athletes have the same biceps circumference they have the same cross-sectional area of muscle.
104
What kind of muscle has fibers that align obliquely with the tendon, creating a featherlike arrangement?
pennate muscle
105
What is defined as the angle between the muscle fibers and an imaginary line between the muscle's origin and insertion?
angle of pennation?
106
Many human muscles are pennated but few have angles of pennation in excess of how many degrees?
15°
107
# Fill in the blank:
The angle of pennation does not remain constant for a given muscle, but increases as the muscle _________.
shortens
108
Muscles with greater pennation have more sarcomeres in a)___________ and fewer sarcomeres in b)____________.
a) parallell
| b) series
109
True or False:
Muscles with greater pennation are better able to generate velocity but have a lower ability to generate force.
False
Muscles with greater pennation are better able to generate force but have a lower maximal shortening velocity than nonpennate muscles because the sarcomeres are arranged in parallel (better suited to generate force).
110
# Fill in the blanks:
Lesser amounts of pennation can be advantageous for producing a)____________ due to the b)_________ number of sarcomeres in c)__________, at the expense of number of sarcomeres in d) __________.
a) high velocities
b) greater
c) series (or in a row)
d) parallel
111
True or False:
Angle of pennation is modifiable through training.
True
112
List 6 muscle fiber arrangements and give an example of each.
1. radiate - gluteus medius
2. longitudinal - rectus abdominis
3. fusiform - biceps brachii
4. multipennate - deltoid
5. bipennate - rectus femoris
6. unipennate - tibialis posterior
113
Why type of muscle fiber arrangement is the gluteus medius?
radiate
114
Why type of muscle fiber arrangement is the tibialis posterior?
unipennate
115
Why type of muscle fiber arrangement is the biceps brachii?
fusiform
116
Why type of muscle fiber arrangement is the rectus abdominis?
longitudinal
117
Why type of muscle fiber arrangement is the deltoid?
multipennate
118
Why type of muscle fiber arrangement is the rectus femoris?
bipennate
119
# Fill in the blanks:
When a muscle is at its resting length, the a)_________ and b)__________ filaments lie next to each other, so that a c)___________ number of potential d)___________ sites are available.
a) actin
b) myosin
c) maximal
d) crossbridge
120
True or False:
The muscle can generate the greatest force at it's shortest length.
False
The muscle can generate the greatest force at it's resting length when there are the maximum number of potential acting and myosin crossbridge sites available.
121
# Fill in the blank: greater or lesser
When the muscle is stretched much beyond its resting length, a __________ proportion of the actin and myosin filaments lie next to each other.
lesser
122
# Fill in the blank: greater or lesser
When the muscle contracts too much below its resting length, a __________ proportion of the crossbridge sites are available.
lesser
The actin filaments overlap when the muscle shortens which reduces the number of crossbridge sites.
123
True or False:
The fewer potential actin and myosin crossbridge sites available decreases force generation capability.
True
124
True or False:
All body movements, even those occurring in a straight line, take place by means of rotation about a joint or joints.
True
125
# Fill in the blank:
The force that muscles produce when rotation about a joint occurs is manifested as ___________.
torque
126
# Fill in the blank: higher or lower
A ___________ value indicates a greater tendency for the applied force to rotate the limb or body part about a joint.
higher
127
True or False:
When speaking of torque versus joint angle, the amount of torque that can be exerted about a given body joint varies throughout the joint's range of motion.
True
128
True or False:
Force capability of muscle declines as the velocity of contraction increases.
True
129
Describe a human movement technique wherein one can make the best of the relationship between the force capability of a muscle declining as the velocity of the contraction increases.
As a vertical jump begins, the arms swing upward, exerting downward force on the body at the shoulders, slowing the upward movement of the body, and forcing the hip and knee extensor muscles to contract more slowly than they otherwise would, enabling them to generate higher forces for longer times.
130
Define concentric muscle action.
The muscle shortens because the contractile force is greater than the resistive force. The forces generated within the muscle and acting to shorten it are greater than the external forces acting at its tendons to stretch it.
131
Define eccentric muscle action.
The muscle lengthens because the contractile force is less than the resistive force. The forces generated within the muscle and acting to shorten it are less than the external forces acting at its tendons to stretch it.
132
Define isometric muscle action.
The muscle length does not change, because the contractile force is equal to the resistive force. The forces generated within the muscle and acting to shorten it are equal to the external forces acting at its tendons to stretch it.
133
Cycling and swimming almost exclusive use what type of muscle action?
Concentric muscle action.
134
The lowering phase of any resistance exercise uses what type of muscle action?
Eccentric muscle action.
135
A sit-up with the trunk held straight uses what type of action muscle in the abdominals?
Isometric muscle action.
136
A curl up sit-up, what two types of muscle actions are used in the abdominals?
Concentric in the raising phase and eccentric in the lowering phase.
137
True or False:
Muscle torque does not vary with joint angular velocity according to the type of muscular action.
False
138
The greatest muscle force can be obtained during what type of muscle action?
eccentric
139
Define strength-to-mass ratio.
The ratio of the strength of the muscles involved in the movement to the mass of the body parts being accelerated.
140
True or False:
The strength-to-mass ration does not directly reflect an athlete's ability to accelerate his or her body.
False
141
# Fill in the blank: increased or reduced
If, after training, an athlete increases body mass by 15% but increases force capability by only 10%, the strength-to-mass ration, and thus the athlete's ability to accelerate, is ___________.
reduced
142
Why is it normal for the strength-to-mass ratio of larger athletes to be lower than that of small athletes?
When body size increases, muscle volume (and body weight) increases proportionally more than does muscle cross-sectional area (and concomitantly strength).
143
True or False:
All else being equal, larger athletes are stronger pound for pound than smaller athletes.
False
Smaller athletes, pound for pound, are stronger than larger athletes. This is because a muscle's maximal contractile force is proportional to its cross-sectional area whereas a muscle's mass is proportion to its volume. As body size increases, body mass increases more rapidly than does muscle strength. The smaller athlete, given constant body proportions, has a higher strength-to-mass ratio than does the larger athlete.
144
Define the classic formula.
The classic formula is used to compare the performance of athletes in different weight categories taking into account the expected drop in the strength-to-mass ratio with increasing body size. The formula is the load lifted divided by the body weight to the 2/3 power. This accounts for the relationship of cross-sectional area versus volume.
145
List the sources of resistance to muscle contraction.
1. gravity
2. inertia
3. friction
4. fluid resistance
5. elasticity
GIFFE
146
An objects's weight is equal to what?
The object's mass times the local acceleration due to gravity.
147
# Fill in the blanks: mass or force
The pound is a unit of a)__________, not b)_________.
a) force
| b) mass
148
The kilogram designation on a weight plate refers to it's what?
mass (not weight)
149
True or False:
It is correct to say that an object weighs a certain number of kilograms.
False
Weight refers to force not mass. Kilograms refers to an object's mass. Pounds refers to an object's weight.
150
True or False:
The moment arm of a weight isn't always horizontal.
False
The moment arm, by definition, by which a force produces torque is perpendicular to the line of action of the force.
151
# Fill in the blank:
The _________ due to an object's weight is the produce of the weight and the horizontal distance from the weight to the pivot point (joint).
torque
152
True or False:
During an exercise, although the weight does not change, its horizontal distance from a given joint axis changes constantly.
True
153
# Fill in the blanks: farther or closer
When the weight is horizontally a)__________ to the joint, it exerts less resistive torque. When it is horizontally b)_________ from a joint, it exerts more resistive torque.
a) closer
| b) farther
154
True or False:
In an arm curl, the horizontal distance from the elbow to the barbell is greatest when the forearm is horizontal. In that position the athlete must exert the greatest muscle torque to support the weight.
True
155
True or False:
Exercise technique can affect the resistive torque pattern during an exercise and can shift stress among muscle groups.
True
156
Describe how one can shift stress among muscle groups in a back squat and how the shift affects the resistive torque patterns of the glutes and the quads.
A more forward inclination of the trunk brings the weight horizontally closer to the knees which reduces the resistive torque about the knees that the quads must counteract. The quads don't have to exert as much force. With the forward inclination of the trunk, the weight is horizontally farther from the hip which increases the resistive torque about the hip that the glutes and hamstrings must counteract. The glutes and hamstrings have to produce more force and work harder.
157
List 3 advantages of weight-stack machines.
1. safety
2. design flexibility - machines can be designed to provide resistance to body movements that are difficult to resist with free weights
3. ease of use
158
List 3 advantages of free weights.
1. whole-body training - a larger portion of the body's musculature and skeleton is taxed
2. free weights force muscles to work in stabilization as well as support
3. simulation of real-life activities
159
True or False:
Inertial force acts only downward.
False
Gravity only acts downward. Inertial force can act in any direction.
160
# Fill in the blank:
In addition to gravitational force, a barbell or weight stack, when accelerated, exerts ___________ on the athlete.
inertial force
161
Define the bracketing technique.
The athlete performs the sport movement with less than normal and greater than normal resistance. This is a form of acceleration training.
162
Using the shot-put as an example, list the advantages and disadvantage of training using the bracketing technique.
PRO: using a heavier load develops greater forces during the accelerative movement than when using the normal shot because the inertia of the heavier implement forces the muscle to contract at relatively low speed.
PRO: using a lighter load, the lower inertial of the shot enables the putter to accelerate the shot more rapidly and to reach a higher speed of release, training the neuromuscular system to operate within desired acceleration and speed ranges.
CON: changes in loading could the technique in a less positive way as the body adjusts with a different motor pattern according to the load used.
163
Define friction.
Friction is the resistive force encountered when one attempts to move an object while it is pressed against another object.
164
# Fill in the blank:
____________ is the resistive force encountered when one attempts to move an object while it is pressed against another objection.
Friction
165
What exercise devices use friction as the main source of resistance?
belt or brake-pad-resisted cycle ergometers and wrist curl devices.
166
True or False:
All else being equal, it takes less force to initiate movement between two surfaces in contact than to maintain previously initiated movement.
False
It takes more force to initiate movement.
167
# Fill in the blanks:
A weighted sled used in training for football or track is an example of a device that is resisted by both a)_________ and b)___________.
a) friction
| b) inertia
168
Using the weighted sled as an example, the resistance due to the sled's inertia is directly proportional to what two variables?
1. the sled's mass
| 2. sled's acceleration
169
What is the advantage of using a weight sled for resistance training?
A weighted sled provides horizontal resistance that cannot be directly provided by weights.
170
Does friction resistance change as speed increases?
No. Once the sled is moving the coefficient of sliding friction stays relatively constant.
171
Does power output increase with speed?
Yes. During the transition from a lower to higher speed there is added resistance due to acceleration.
172
Define fluid resistance.
The 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.
173
Name sport activities in which fluid resistance is a significant factor.
1. Swimming & rowing (water resistance)
| 2. Golf, sprinting, discus throwing, and baseball pitching (air resistance)
174
Name the two sources of fluid resistance.
1. surface drag - results from the friction of a fluid passing along the surface of an object
2. form drag - results from the way in which a fluid presses against the front of rear of an object pass through it.
175
What do fluid-resisted exercise machines most often use to generate resistance?
cylinders in which a piston forces fluid through an opening as the exercise movement is performed.
176
List 3 variable in which a fluid-resistance exercise machine produces greater resistance.
1. the piston is pushed faster
2. the opening through which the fluid flows is smaller
3. the fluid is more viscous
177
# Fill in the blank:
All else being equal, fluid resistive force is roughly proportional to the _____________.
Velocity of piston movement
178
True or False:
Fluid-resisted machines do not generally provide a concentric exercise phase of the muscles.
False
Fluid resisted machines do not generally provide an eccentric phase but they may if they incorporate an internal pump.
179
What is the difference between fluid-resisted machines and free weights on muscle actions?
Free weights (or weight machines) involve alternate concentric and eccentric actions of the same muscle with little or not rest in between.
Fluid-resisted machines generally involve alternate concentric actions of antagonistic muscle groups; each muscle group rests while its antagonist works.
180
List some sport movements that may not benefit from fluid-resisted exercise machines and explain why.
Due to the lack of eccentric muscle action with fluid-resisted exercise machines, there would be less than optimal specificity of training for sport movements that involve eccentric muscle actions such as running, jumping and throwing.
181
List some elastic components in exercise devices that provide elasticity as the primary source of resistance.
Springs, bands, bows and rods.
182
The resistance provided by a standard elastic component is proportional to what variable?
The distance it is streched.
183
True or False:
The more the elastic component is stretched, the greater the resistance.
True
184
What is the major problem with devices using elastic resistance with regards to resistive force.
Every exercise movement begins with low resistance and ends with high resistance which is contrary to the force capability patterns of virtually all human muscle groups, which show a substantial drop-off in force capability toward the end of the range of motion.
185
Using vertical jumping as an example, why would using elastic resistance in vertical jumping be less than ideal?
The elastic bands provide little resistance early in the jump when the large gluteus and quadriceps muscles are capable of exerting great force. The bands provide the greatest resistance while the jumper is in the air -- serving mainly to pull the jumper back to the ground, rather than resist the muscle and to increase the rate at which the jumper hits the ground on landing, which may increase injury risk.
186
High, Intermediate, or Low: Rate the risk of injury for the following:
1. running & aerobics
2. cycling, walking and resistance training
3. team sports
1. intermediate
2. low
3. high
187
True or False:
The risk of injury from resistance training is low compared to that of other sport and physical conditioning activities.
True
188
# Fill in the blanks:
a) advantage or disadvantage
b) greater than or less than
Back muscles at a great mechanical a)___________ and must generate forces b)____________ the weight of an object lifted.
a) disadvantage
| b) greater than
189
True or False:
Our intervertebral disks are under compressive force even when we are merely standing, sitting, walking, or running -- and even under more compressive force when we are lifting and carrying.
True
190
True or False:
Spinal internal loads are variable with varying postures during the lift and that deep squatting positions with load are not necessarily associated with back injury.
True
191
# Fill in the blank:
85% to 90% of all intervertebral disk herniations occur at the disks between a)____ & _____ and at the disks between b)_____ & _____.
a) L4 & L5
| b) L5 & S1
192
True or False:
When a weight is supported in the hands or on the shoulders and the trunk is inclined forward, there is great torque about the lower intervertebral disks due to the large horizontal distance between the lower back and the weight.
True
193
Explain why back muscles operate at a mechanical disadvantage when a weight is supported in the hands or on the shoulders and the trunk is inclined forward during, for instance, a squat.
The perpendicular distance from the line of action of the spinal erector muscles to the intervertebral disks is much shorter than the horizontal distance from the weight to the disks. As a result the muscles must exert forces that can exceed 10 times the weight lifted. These forces act to squeeze the intervertebral disks between the adjacent vertebral bodies and can lead to injury.
194
True or False:
A normal lordotic lumbar spine position is inferior to a rounded back for avoiding injury to vertebrae, disks, facet joints, ligaments, and muscles of the back.
False
A normal lordotic spine position is superior to a rounded back for reducing injury. Low back muscles are capable of exerting higher forces when the back is arched rather than rounded.
195
# Fill in the blanks:
The vertebral column is naturally S-shaped, being slightly rounded (a. _____________) in the thoracic spine and b. ____________ in the lumber spine.
a. kyphotic
| b. lordotic
196
Define ventral.
Toward the anterior or front.
197
Define dorsal.
Toward the posterior or back.
198
When the lower back is rounded, which edges of the vertebral bodies squeeze which portions of the intervertebral disks?
anterior (ventral) edges of vertebral bodies squeeze the front portions of the intervertebral disks.
199
In extreme arching of the back, which edges of the vertebral bodies squeeze which portions of the intervertebral disks?
posterior (dorsal) edges of vertebral bodies squeeze the posterior portions of the intervertebral disks.
200
True or False:
Resistance training exercises should generally be performed with the lower back in a moderately arched position to reduce risk of damage to the disks.
True
201
True or False:
The abdomen is composed mainly of fluid and normally contains very little gas, it is virtually incompressible.
True
202
What is the "fluid ball?"
The tensing of surrounding muscle (deep abdominal muscles and diaphragm) aids in supporting the vertebral column during resistance training by keeping the abdominal fluids and tissue under pressure.
203
How does the support of the "fluid ball" help with the back during resistance training?
The added support of the tensing of the deep abdominal muscles and diaphragm can significantly reduce both the forces required by the erector spinae muscles to perform an exercise and the associated compressive forces on the disks.
204
Define intra-abdominal pressure.
The tensing of the deep abomdinal muscles and respiratory diaphragm in order to support the vertebral column by keeping the abdominal fluids and tissue under pressure.
205
Define Valsalva maneuver.
A method of generating intra-abdominal pressure where the glottis is closed, keeping air from escaping the lungs, and the muscles of the abdomen and rib cage contract, creating rigid compartments of liquid in the lower torso and air in the upper torso. The VM increases the rigidity of the entire torso, making it easier to support heavy loads.
206
True or False:
The Valsalva Maneuver is necessary for generation of intra-abdominal pressure.
False
The VM is one way of doing it but not the only way.
207
What is the downside of using the Valsalva maneuver?
Pressure in the chest (pressurizing the chest compartment) associated with the Valsalva maneuver can exert compressive force on the heart, making it more difficult for blood to return to the heart. It can also transiently raise blood pressure to slightly elevated levels.
208
What are the two ways of creating intra-abdominal pressure and which one is regarded as being the safer way.
1. Valsalva maneuver using a closed glottis (breath is held) creating more pressure in the chest. This method can lead to blackout.
2. using open glottis while still supporting the lower spine does not pressurize the chest compartment and is regarded as the safer method.
209
True or False:
Weightlifting belts have been shown to increase intra-abdominal pressure during resistance training.
True
210
Why would using a weightlifting belt for all exercises be less than optimal way to train?
The abdominal muscles that produce intra-abdominal pressure might not get enough training stimulus to develop optimally.
211
What are 3 conservative recommendations for using weight belts?
1. A weight belt is not needed for exercises that do not directly affect the lower back.
2. For exercises directly stressing the back, refrain from wearing a belt during lighter sets but use one for near-maximal and maximal sets.
3. Just never use a weight lifting belt and build up the strength of the back muscles and the muscles that generate intra-abdominal pressure in a gradual and systematic manner.
