Chapter 2--Biomechanics

Question 1

Biomechanics

Answer 1

mechanisms of the musculoskeletal system as it relates to movement

Question 2

Agonist

antagonist

Synergist

Answer 2

muscle most directly involved in movement; prime mover

can slow down or stop the movement

assist indirectly in movement; required to control body motion when the agonist crosses two joints

Question 3

Sagittal

frontal

transverse

Answer 3

movement takes place in forward/backward motion
flexion and extension

movement takes place in lateral, side/side motion
adduction and abduction

movement takes place in a rotational movement parallel to the ground
internal/external rotation

Question 4

1st class lever

2nd class lever

3rd class lever

Answer 4

muscle force and resistive force act on opposite sides of the fulcrum (forearm)

muscle force and resistive force act on the same side of the fulcrum with muscle force acting through a longer moment arm

muscle force and resistive force at on the same side of the fulcrum with muscle force acting through a shorter moment arm

Question 5

Fulcrum

lever

torque

Answer 5

pivot point

rigid 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

magnitude of force times the length of its moment arm

Question 6

mechanical advantage

Answer 6

ratio of moment arm of the applied force to that of a resistive force

ratio greater than 1.0 allows for less muscle force than the resistive force to produce an equal amount of torque

ratio less than 1.0 indicates the need to apply greater muscle force than the resistive force, creating a disadvantage for the muscle

most muscles that rotate the limbs about body joints operate at a mechanical advantage less than 1.0

Question 7

moment arm

Answer 7

perpendicular distance from the line of action of the force to the fulcrum

Question 8

Tendon insertion

Answer 8

all other factors equal, a person whose tendons are inserted on the bone farther from the joint center should be able to lift heavier weights because the moment arm of the muscle force is longer and can produce greater torque

this mechanical advantage is also accompanied by a loss of max speed because the muscle has to contract more to make the joint move through a given range of motion

muscle inserted farther away must contract at a higher speed which generates less force (inverse force-velocity relationship in muscle) muscle’s force capability is reduced during faster movements

for slower movements, like powerlifting, tendon insertion farther from the joint than normal can be advantageous, but for athletic activities at high speeds, like hitting a tennis ball, it is disadvantageous

Question 9

strength

acceleration

power

work

Answer 9

ability to exert force

change in velocity per unit time

time rate of doing work (force x velocity)

product of the force exerted on an object and the distance it moves in the direction of the force

Question 10

negative work and power

Answer 10

occur during eccentric muscle action

refers to work performed on, rather than by muscles

rate at which the reps are performed determines the power output

Question 11

neural control

Answer 11

affects the max force output of a muscle by determining which and how many motor units are involved in the contraction (recruitment)

affects the rate at which the motor units are fired (rate coding)

Question 12

muscle force is greater when

Answer 12

more motor units are involved

motor units are greater in size

rate of firing is faster

Question 13

the force a muscle can exert

Answer 13

is related to its cross-sectional area rather than its volume

Question 14

pennation

Answer 14

fibers aligned obliquely with the tendon

muscles with greater pennation have more sarcomeres in parallel and fewer sarcomeres in series; they are better able to generate force but have lower max shortening velocity

less pennation is better for producing high velocities

angle of pennation is modifiable through training

Question 15

Weight stack machines

Answer 15

safety
design flexibility
ease of use

Question 16

free weights

Answer 16

whole body training

simulation of real-life activities

Question 17

valsalva maneuver

Answer 17

glottis is closed holding air in the lungs
muscles are contracted in abdomen and rib cage
rigid compartments of air and liquid are created in upper and lower torso

side effects=exerts compressive forces on heart making it difficult for blood to return, raises blood pressure

Question 18

classic formula

Answer 18

divides the load lifted by the athlete’s body weight to the 2/3 power

Question 19

during a free weight exercise, muscle force varies with

Answer 19

perpendicular distance from the weight to the body joint and movement acceleration

Question 20

vertical jump involves knee, hip and shoulder movement in the

Answer 20

sagittal plane

Question 21

a concentric elbow flexion and extension exercise involves which types of levers at the elbow

Answer 21

first class during extension and 3rd class during flexion

Question 22

Formation of new bone

Answer 22

select exercises that are ground-based, multi-joint movements
load the spine through movements of the hips, knees and ankles
place high forces on the body via high-intensity impact movements such as plyometrics and sprinting

Question 23

tendons and ligaments increase in their ability to withstand force by

Answer 23

increases in diameter of the fibrils
cross-links occur at higher rates
new collagen fibers develop

ground-based multi-joint movements at high intensities and with full range of motion
no adaptations occur at low to mod intensities