Biomechanics

Question 1

Sport Biomechanics

Answer 1

Sport biomechanics: is the study of human motion. It studies the effect of forces and motion on sport performance, using laws and principles grounded in physics that applied to human movement.

Advantages of Sport Biomechanics:
- When coaches and athletes understand how forces work on muscles and affect motion in sports, they have a clear advantage over those who lack the knowledge and its application. When you understand this and know the basic concept, you have a better rationale for learning the correct way to execute.

Anatomy and physiology lay foundation for biomechanics and kinesiology, areas of study about human movement with a command of these areas coaches can:
1. Analyse sport movement
2. Select the best training exercises
3. Reduce or prevent injuries
4. Design or choose the sport equipment that best matches athletes personal needs
5. Maximise economy and efficiency of movement

Question 2

Clinical Biomechanics

Answer 2

Is the application of biomechanics to the treatment of patients.

Clinical biomechanics explores facets of body systems, organs, tissue and cell biomechanics with an emphasis on medical and clinical application of the basic science aspects.

Question 3

Occupational Biomechanics

Answer 3

Occupational biomechanics is the study of movement related to the act of performing occupational duties.

Occupational movement may help workers to be more efficient, healthier and happier in their everyday processes.

Question 4

Sub-Branches of Biomechanics

Answer 4

What is Balance:
Balance is the ability to control equilibrium static or dynamic with human movement.

Equilibrium:
Refers to a state of zero acceleration where there is no change on the speed or direction of the body

Static Balance:
IS out ability to hold our body in a specific position and posture.

Dynamic Balance:
Is out ability to maintain balance while moving our body and walking.

Question 5

Qualitative and Quantitative approaches to Biomechanics

Answer 5

Qualitative:
1. Observation of form and execution
2. Mirrors
3. Video recording
4. Performance

Quantitative:
1. Speed
2. Accuracy
3. Deliverance
4. Distance covered
5. How high (vertical distance)
6. Reaction time

Question 6

Principles of Movement

Answer 6

Understanding the dynamics of movement in sport is essential for athletes and coaches to arrive at the level of proficiency that is expected of them.

Analysis of movement can be used to identify shortcomings in the athletes and also take corrective action. All body movement can be described using a combination of standard terms of reference, these include the type of muscular action that creates movement (concentric and eccentric), the direction of body part that moves relative to its joint (flexion and extension) and the planes of which movement occurs.

Question 7

Components of movement

Answer 7

The components of movement include;
- Force
- Linear motion
- Rotational motion
- Velocity
- Acceleration
- Momentum

Question 8

Force

Answer 8

Force is the push or pull exerted on an object or body which may either cause motion on a stationary body or a speeded or slowing down or change of direction of a moving body.

Force can either be internally generated via muscular contraction or eternally through the action of gravity, friction and the forces or air and water.

One newton represents the force required to give a 1 kilogram mass an acceleration of 1m/ sx2 of 1 mc2

Question 9

Linear Motion

Answer 9

This is movement along a straight line. Objects not subjected to forces will continue to move uniformly in a straight line indefinitely.

Linear motion is measured in two parts speed and direction.

Speed is a scalar quantity where direction is not considered. When considering linear motion biomechanics normally require a direction and velocity is a vector quantity and has both size and direction.

Speed = distance travelled divided by time taken

Velocity = displacement divided by time taken

Both are measured in meters travelled per second (1m/s)

Question 10

Acceleration

Answer 10

This tells us how fast the velocity of something changes, as such is a vector quantity possessing both magnitude and direction.

Acceleration = change in velocity over time taken

Question 11

Newton’s First Law- Inertia

Answer 11

An object at rest remains at rest, and an object in motion remains in motion at constant speed and in a straight line unless acted on by an unbalanced force.

Question 12

Newton’s Second Law- Acceleration

Answer 12

The acceleration of an object is directly proportional to the force causing it and it is inversely proportional, to the mass of the object and the acceleration takes place in the direction on which that force acts.

Question 13

Newton’s Third Law

Answer 13

When one object exerts a force on a second object there is a force equal in magnitude but opposite in direction exerted by the second object on the first.

Reaction force = the weight force + internal muscular force

Example: a footballer kicking a ball exerts a force upon it in order to set it in motion. According to newton’s third law the ball will exert an equal but opposite force on the kicking foot.

Question 14

Momentum

Answer 14

Is the amount of motion a moving object has and is the product of its mass and velocity. (MO = Mass x Velocity)

A body’s momentum can be changed by altering either its mass or velocity. However, in sporting activity the mass of a body or object generally remains constant therefore any change in momentum must be due to change in velocity.

Example: a long jumper may increase velocity by changing their run up in order to increase their momentum before takeoff. Once in the air the velocity and mass of the jumper remains constant so momentum is said to be conserved.
This extends Newton’s First Law of motion.

Question 15

Impact

Answer 15

Momentum becomes more important in sporting situations where collisions or impacts occur. The outcome of the collision depends largely upon the amount of momentum each of the bodies possessed before the collision takes place. The body with greater momentum will be more difficult to stop. A change in momentum is synonymous with a change in acceleration and as such relates to Newton’s second law.

Question 16

Impulse

Answer 16

This suggests that any change in momentum is dependent upon the product of the force and the time that that force is applied to an object is known as impulse.

Example: A follow through of a racket will ensure that the time over which the force has been applied os at its maximum the change in momentum or acceleration of the ball will be greater than if a follow through had not been performed.

Question 17

Fluid Forces

Answer 17

Gravity: Is an external force that naturally occurs and pull a body or object towards the center of the earth.

Newton’s Law of gravitation states all particles attract one another with a force proportional to the product of their masses, and inversely proportional to the square of the distance between them.

Center of Mass:
An important feature of gravitational pull is that it always occurs through the center of mass or weight of an object, which is where the weight tends to be concentrated. This point signifies that point above which the object or body is balanced in all directions.

Athletes and coaches can use their knowledge of this concept in order to improve performance.

If the center of mass is lowered or the base of support is increased, the more stable the object or body. For example, a judo player has a wide stance in order to resists attacks from their opponents.

Question 18

Levers and their Functions

Answer 18

Efficient and effective movement is made possible by a system of levers. These are mechanical devices used to produce the turning motion about a fixed point and is used to apply force against a resistance. In the human body, bones act as levers, joints act a full crown and the muscles act as the effort and the weight of the body part, plus anything that it holds is the resistance.

First Class Levers:
The fulcrum lies between the effort and the resisting force. The head is a good example of the action of a first class lever in the body, when the head and neck are being flexed and extended as in nodding.

Second Class Levers:
The resistance lies between the fulcrum and the effort. An example of this is when you raise up your toes where the toes are in contact with the floor is the fulcrum.

Third Class Levers:
The effort is between the fulcrum and the load. In terms of applying force this is a very inefficient lever, but it allows speed and range of movement. This is the most common form of lever in the body. The majority of movement in the body is controlled by third class levers.

Question 19

Functions of levers

Answer 19

1. To increase the resistance that a given effort can move
2. To increase the speed at which a body moves

First class levers can increase the speed of a body, second class levers tend to increase the effect of the effort force.

Third class levers can be used to increase the speed of a body. an example of third class lever is the action of the hamstrings and quadriceps on the knee joint, which causes flexion and extension of the lower leg.

Question 20

Eccentric and Concentric Force

Answer 20

Eccentric:
This offcentered force is called eccentric force and is vital for rotation to occur. When the force is applied through the center of mass the resulting motion will be linear, but when the force is applied outside the center of gravity the resulting motion will be linear, but when the force is applied outside the center of gravity the resulting motion will be angular.

Concentric:

Question 21

Angular Motion, Displacement, Velocity and Acceleration

Answer 21

Angular Motion:
Quantities used to explain linear motion are also applied to angular motion: displacement, velocity and acceleration. However, in rotating bodies we consider these quantities in their angular forms, namely displacement, angular velocity and angular acceleration.

Angular Displacement:
Just as the distance traveled by the body moving linearly can be measured, so can the distance of an object rotating around an object. Angular displacement is usually measured in degrees, where there is one complete rotation the body would have passed through 160 degrees. If the direction is stated when describing angular distance, the term angular displacement is used.

Angular Velocity:
The angular velocity of a body is the angle through which a body rotates about an axis in one second. It is calculated as the angle described in a given time divided by that time. The standard unit for angular motion is radians per second (rad/sec).

Angular Acceleration:
This is the rate of change of angular velocity and is measured in radians per second squared (rad/sec2)

Question 22

Moment of Inertia

Answer 22

The moment of inertia of a body is its resistance to rotational or angular motion. When already rotating the moment of inertia is the resistance of a body to change in the state of rotation; this can be compared to its linear counterpart.

The moment of inertia of a body is determined by its mass and the distribution of its mass around the axis of rotation. The further its mass is away from the axis, the greater its moment if inertia and the more force is required to make it spin or stop it spinning of rotation is already occurring.

It can be calculated as the following:
moment of inertia = mass of body part x distance from the axis of rotation squared.

Question 23

Newton’s Laws of Angular Motion

Answer 23

Newton’s First Law of Angular Motion:
A rotating body will continue to turn about its axis of rotation with constant angular momentum unless an external couple or eccentric force is exerted upon it.

Newton’s Second Law of Angular Motion:
The angular acceleration of a body is proportional to the torque causing it and takes place in the direction in which the torque acts. By increasing a turning effect or torque greater angular acceleration can be achieved.

Newton’s Third Law of Angular Motion:
For every torque that is exerted on one body by another there is an equal and opposite torque exerted by the second body on the first

Question 24

Motor Programmes

Answer 24

The traditional view of a motor programme was that it was a centrally organized re-planned set of very specific muscle commands that when initiated allowed the entire sequence of movement to be carried out without reference to additional feedback. This view help to explain how performers sometimes appear able to carry out very fast actions that have been well learned without really thinking about the action almost automatic.

Question 25

Open and Closed Lopp Control

Answer 25

Open Loop:
Motor programmes or pre-learned mastered movements initiated on command are thought to be developed through practice. A series of movements built up, starting with very simple movements until certain actions are stores as complete movements. These complete movements or motor programmes can be stored in long term memory and retrieved at will, the whole movement to be carried out can then be initiated by one complete compound. It is suggested that such skills are built up in a hierarchy of schematic ways.

Closed Loop Control:
Within the closed loop model the loop is completed by information from the various sensory receptors feeding back information to the central mechanisms. Why is it accepted that there are many types of feedback? In this view of feedback control is internal, allowing the performer to compare what is actually happening during the movement with a point of reference namely the correct or currently learned and stored motor performance. This evaluation of the movement currently being undertaken means errors, if any, can be detected and corrected. All feedback goes through the processing system which means that the processes of detecting and correcting errors are relatively slow.

Research has shown that the closed loop system of movement control generally works more effectively with movement taking place over a long period of time or skill requiring slower limb movements. Closed loop models are nit thought to be effective for controlling quick discreet type movement.

Question 26

Schema Theory

Answer 26

It was stated earlier that motor programmes were traditionally considered to be specific set of pre-organized muscle commands that control the full movement. This suggests that specific motor programmes for all possible types of actions are stores in the long term memory awaiting selection and initiation. If we accept that motor programmes operate via continuously changing closed and open loop control, it is the stored motor programmes which either direct all movements or is used as a point of reference for a movement to be compared against.

Jack Adam believed that motor programmes are made up of 2 areas of stored information:
1. The memory trace- used for selecting and initiating movement, operating as an open loop system of control prior to the perceptual trace. it does not control movement.
2. The perceptual trace- used as the point of reference (memory of past movement) and also to determine the extent of movement in progress. Thus the perceptual trace is operating as a closed loop system of control making the ongoing necessary adjustment where and when needed.

Question 27

Schmidt Schema Theory

Answer 27

Schmidt presented his well known schema-theory as a wat of dealing with the limitations, as he saw them, of Adams’ closed loop theory. Schmidt proposed that schemas, rather than the memory and perceptual traces suggested by Adams, explained recall of movement pattern. Instead of there being very specific traces for all learned or experienced movement, schemas as Scmidt saw them were ‘a rule or set of rules that serve to provide the basis for a decision.’

These generalised patterns or rules of movement solved the following dilemma:
1. How do we store possibly thousands, if not millions, of specific programmes of movement
2. How do we initiate and control fast and more complex movements.

Schmidt suggested that we learn and control movements by developing generalised patterns of movement around certain types of movement experience. e.g. catching, throwing; rather they collate various items of information every time they experience either catching or throwing. This helps in building up their knowledge of catching or throwing in general. Performers thus construct schemas which enable them at some future time to successfully carry out a variety of movement.

Question 28

Strategies/ Methods to enable Schema to Develop

Answer 28

1. Varied practice conditions
2. Avoid blocked or massed practice
3. Practice relevant to the game (opposition)
4. Include plenty of feedback- continuous and terminal
5. Realistic practice
6. Tasks should be challenging/ gradually more difficult
7. Slow motion practice
8. Include transferable elements