ES - Basic Principles of Biomech. Regarding... - Kinetic Laws and Principles of Movement

Question 1

Three types of levers in the body

Answer 1

first-, second-, and third-class levers

Question 2

First class lever and example

Answer 2

muscle force and resistive force act on opposite sides of the fulcrum
ex. forearm during tricep pushdowns

Question 3

Second class lever and example

Answer 3

muscle force and resistive force act on same side of fulcrum, with muscle force acting through a moment arm longer than that through which the resistive force acts.
ex. calf raise

Question 4

Third class lever and example

Answer 4

muscle force and resistive force act on same side of the fulcrum, with muscle force acting through a moment arm shorter than that through which the resistive force acts.
ex. bicep curl

Question 5

Mechanical advantage of all levers and impact on muscle force production

Answer 5

First: , or = 1.0
Second: always greater than 1.0
Third: always less than 1.0
Determines how much muscle force is needed to move a resistive force for a given level.

Question 6

Lever A.R.M.

Answer 6

A: Axis is in the middle - first class lever
R: Resistance is in the middle- second class
M: Muscle force is in the middle - third class

Question 7

How does mechanical advantage affect force production?

Answer 7

<1.0 = a person must apply greater muscle force than the amount of resistive force, disadvantage
>1.0 = a person can apply less muscle force than the resistive force to produce an equal amount of torque.
= 1.0 = muscle force applied equals resistive force (??????)

Question 8

What biomechanical factors effect strength? (9)

Answer 8

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

Question 9

Neural Control

Answer 9

affects maximal force output of a muscle by determining which and how many motor units are involved in a muscle contraction (recruitment) and rate at which motor units are fired (rate coding).

Question 10

Neural Control: When muscle force is greater when (3)

Answer 10

More motor units are involved in a contraction
Motor units are greater in size
Rate of firing is faster

Question 11

Neural Control: Much of the improvement in strength evidenced in the first _____ weeks of resistance training is attributable to…

Answer 11

few; attributable to neural adaptations as the brain learns how to generate more force from a given amount of contractile tissue.

Question 12

Muscle Cross-Sectional Area

Answer 12

all else being equal, the force a muscle can exert is related to its cross-sectional area rather than to its volume.
ex. if 2 athletes of similar BF% but different heights have same biceps circumference, their upper arm muscle cross-sectional areas are about the same. Although the taller (therefore heavier) athlete’s longer muscle makes for greater muscle volume, the strength of the two athletes’ biceps should be about the same.

Question 13

With same strength but different body weight, a taller athlete has less ability to ____ and _____ their own body.
Resistance training increases both ________ and ________ of muscle

Answer 13

lift and accelerate.
strength and cross-sectional area.
ex. gymnasts are small

Question 14

Arrangement of Muscle Fibers (AMF)

Answer 14

Maximally contracting muscles have been found capable of generating forces of 23-145 psi (16-100 N/cm2) of muscle cross-sectional area.
This wide range can be partially accounted for by the variation in the arrangement and alignment of sacromeres in relation to the long axis of the muscle.

Question 15

AMF: Pennate Muscle

Answer 15

has fibers that align obliquely w/ the tendon, creating featherlike arrangement.

Question 16

Angle of Pennation

Answer 16

angle between muscle fibers and an imaginary line between muscle origin and insertion, 0 degree corresponds to no pennation.
Many muscles are pennated, but few have angles of pennation >15 degrees.
Increases as muscle shortens and does not stay constant.
Thus, any factor that affects angle of pennation will affect strength and velocity of shortening as long as cross-sectional area remains the same.

Question 17

Muscles w/ ______ pennation have ______ sacromeres in parallel and ______ sacromeres in series…

Answer 17

Muscles w/ greater pennation have more saromeres in parallel and fewer sacromeres in series.
They are therefore better able to generate force but have a lower maximal shortening velocity than nonpennate muscles.

Question 18

Lesser amounts of pennation can be advantageous for producing…

Answer 18

high velocities due to the greater number of sacromeres in a row, at the expense of number of sacromeres in parallel.
Amount of pennation has an effect on muscle ability to generate eccentric, isometric, or lo-speed concentric force.

Question 19

Angle of pennation is modifiable through…

Answer 19

training, which could help account for some of the differences in strength and speed seen in those who have muscles of same size.

Question 20

Muscle Length

Answer 20

Resting length: actin and myosin filaments lie next to each other, so that a maximal number of potential cross-bridge sites are available. Thus, the muscle can generate max force at resting length.

Stretched beyond resting length: a smaller portion of actin and myosin lie next to each other, so there are fewer potential cross-bridge sites. Thus, the muscle cannot generate as much force as it can at resting length. This is b/c actin overlaps when stretched muscle contracts, reducing cross-bridge sites, thus decreasing force capability.

Question 21

Joint Angle

Answer 21

All body movements take place by means of rotation about a joint(s), thus forces that muscles produce must be manifested as torques (higher torque = higher tendency for applied force to rotate limb of body part about a joint).

The amount of torque exerted about a given body joint varies throughout the joint’s ROM, largely b/c of force v. muscle length relationship as well as changing leverage of dynamic geometry of muscles, tendons, and internal joints.

Question 22

AMF Types

Answer 22

a

Question 23

Muscle Contraction Velocity

Answer 23

i. e. force-velocity curve; force capability of muscle declines as velocity of contraction increases. The decline in force capability is steepest over the lower range of movement speeds (high force during eccentric movements).
ex. vert. jump begins, arms swing upward (exerting downward forces on body at the shoulders, slowing upward movement of body, and forcing hip and knee extensors to contract more slowly than they otherwise would, enabling them to generate higher forces for long times.

Question 24

Joint Angular Velocity

Answer 24

speed joint moves (rotational speed); muscle torque varies w/ joint angular velocity according to the type of muscle action.
During isokinetic (constant-speed) concentric movements, torque capability declines as angular velocity increases.
During eccentric movements, as joint angular velocity increases, maximal torque capability increase until ~90 degrees/second (1.57 rad/s), after which it declines gradually.

Question 25

Strength-to-Mass Ratio

Answer 25

Ratio directly reflects an athlete’s ability to accelerate their body.
If after training, their body mass increases 15% but only increases force capability by 10%, their ability to accelerate is reduced.
If many athlete’s have a similar body mass, the strongest will have the advantage.
Trial and error can help athletes find a weight in which strength is highest relative to that of other athletes. Once that weight is found, the objective is to then become as strong as possible without exceeding weight class.
Larger athletes have lower S-to-M ratios than smaller athletes b/c when body size increases, muscle volume (i.e body weight) increases more than muscle cross-sectional area (i.e. strength).

Question 26

Body Size

Answer 26

Smaller athletes are stronger pound for pound than bigger athletes b/c muscle’s maximal contractile force is fairly proportional to its cross-sectional area, which id related to the square of linear body dimensions, whereas muscle mass is proportional to its volume, which is related to the cube of linear body dimensions.
Therefore, as body size increases, body mass increases more rapidly than muscle strength.
Given constant body proportions, smaller athlete’s have a higher S-to-M ratio than larger athletes.

Question 27

Classic formula

Answer 27

load lifted / body weight^2/3

determines that performances of medium-weight athletes are usually the best.

Question 28

Difference between Strength and Power

Answer 28

S: ability of muscles to exert force. It’s the capacity to exert force ay any given velocity at whatever speed.

P: time rate of doing work, where work is the product of the force exerted on an object and the distance the object moves in the direction that the force is exerted. The mathematical product of force and velocity at whatever speed.

Question 29

For a sport movement made slow by high resistance, ____ _____ strength is critical.

Answer 29

low-velocity
ex. two linemen push against each other, velocity is slowed by the opposing player pushing back as well as the inertia of the opposing players body mass.

Question 30

For a sport movement that’s fast due to low resistance, _____ ______ strength is critical.

Answer 30

high-velocity
ex. badminton player muscles quickly reach high velocity as a result of minimal inertial resistance of the lightweight racket and player’s arm.

Question 31

Momentum

Answer 31

relationship between mass of an object and the velocity of movement.
ex. generating greater force to cover a greater distance in less time.

Question 32

Torque

Answer 32

aka moment.
Degree to which a force tends to rotate an object about a specified fulcrum.
Defined quantitatively as the magnitude of a force times the length of its moment arm.

Question 33

Work and it’s equation

Answer 33

product of force exerted on an object and the distance the object moves in the direction in which the force is exerted.
Equation: Work = Force x Displacement

Question 34

Power

Answer 34

time rate of doing work

Power = Work/Time

Question 35

Force

Answer 35

Interaction of two physical objects.
Has both magnitude and direction.
Described as push or pull.

Question 36

Muscle Force

Answer 36

force generated by biomechanical activity, or the stretching of noncontractile tissue, that tends to draw the opposite ends of a muscle toward each other.

Question 37

Resistive Force

Answer 37

force generated by a source external to the body (e.g. gravity, inertia, friction) that acts opposite to muscle force.

Question 38

Center of Gravity

Answer 38

point at which all of the body’s mass and weight is equally balanced or equally distributed in all directions.
It is point at which the combined mass of the body appears to be concentrated.

Question 39

Impulse

Answer 39

Product of generated force and the time required for its production, which is measured as the area under the force-time curve.
According to the impulse-momentum relationship, impulse dictates the magnitude of change of momentum of an object.

Question 40

Center of Pressure

Answer 40

Point on a surface where the total sum of the resultant forces can act with the same magnitude of the force which is distributed on the surface of an object. Measuring the COP has been used in biomechanics as a way to measure the postural balance in humans.

Question 41

Force-Velocity curve

Answer 41

Concentric: light resistance = higher velocity, higher resistance = lower velocity. Eventually, as load increases, velocity decreases to zero (isometric contraction).

Eccentric: as resistance increases beyond what the muscles can handle during an isometric contraction, muscle begins to lengthen, resulting in eccentric contraction.
As load continues to increase, muscle will no longer be able to resist, likely dropping the load.

Question 42

Force-Time curve

Answer 42

a

Question 43

Isokinetic

Answer 43

a specific technique that may use any or all of the different type of contractions.
Type of dynamic exercise usually using concentric and/or eccentric muscle contractions in which velocity of movement is constant and muscle contraction occurs throughout the movement.

Question 44

Isotonic

Answer 44

contractions that involve the muscle developing tension to either cause or control joint movement.
Classified as either concentric or eccentric movements..
Dynamic contractions: varying degrees of tension in the muscles.

Question 45

Isometric

Answer 45

occurs when tension developed within muscle but joint angle remains constant.
Static contractions: active tension is developed to maintain joint angle.
Stabilize body