1. CQ3 – How do biomechanical principles influence movement?
PRELIMINARY HSC PDHPE
CQ3 – How do biomechanical principles influence movement?

2. How do biomechanical principles influence movement?
Students learn about:
motion
the application of linear motion, velocity, speed, acceleration, momentum in movement and performance contexts
Students learn to:
apply principles of motion to enhance performance through participation in practical workshops
balance and stability
centre of gravity
line of gravity
base of support
apply principles of balance and stability to enhance performance through participation in practical workshops
fluid mechanics
flotation, centre of buoyancy
fluid resistance
apply principles of fluid mechanics to enhance performance through participation in practical workshops
describe how principles of fluid mechanics have influenced changes in movement and performance, eg technique modification, clothing/suits, equipment/apparatus
force
how the body applies force
how the body absorbs force
applying force to an object.
apply principles of force to enhance performance through participation in practical workshops.

3. Biomechanics
Biomechanics is the area of study in which the knowledge and methods of mechanics are applied to the biological actions and structures of the body. It is concerned with the internal and external forces that act on the body and the movements that these forces produce. Through the study of biomechanics a vast range of professionals, from zoologists to engineers, can measure, explain, categorise and model the movement patterns of bodies and their internal systems.
A thorough understanding of the biological and mechanical aspects of human movement can facilitate better coaching, learning, movement and exercise therapy for humans. The human body is not a machine. Instead, it is an amazing collection of living matter, consisting of over 206 bones, 400 muscles, 43 major joints, 14 billion nerve cells, 100 trillion other cells and blood that travels through km of blood vessels each minute as it circulates the body.

4. Biomechanics

5. Motion
the application of linear motion, velocity, speed, acceleration, momentum in movement and performance contexts

6. the application of linear motion, velocity, speed, acceleration, momentum in movement and performance contexts
The movement or motion of a human body, a human limb or objects propelled by a human body can be described in terms of either a line or a circular pathway. Movement along a line is called linear motion.

7. Linear motion
Linear motion occurs when the human body, a human limb or an object propelled by a human moves in the same direction at the same speed over the same distance; for example, when running. There are two types of linear motion:
• When this movement takes place in a straight line, it is called rectilinear motion.
• When it takes place in a curved path, it is called curvilinear motion.

8. Linear motion

9. Linear motion

10. Kinematics is the branch of biomechanics that describes how far, how fast and how consistently a body moves. Kinetics is concerned with what causes a body to move the way it does.
In Figure 6.3:
• The linear distance that the runner travels from the start to the finish— Start to A to B to C to D to Finish—is the actual length of the path travelled.
• The linear displacement is the length of the straight line between the start and the finish.

11. Motion can also be classified as angular or rotary
Motion can also be classified as angular or rotary. This type of motion occurs when the human body, a human limb or an object propelled by a human moves along a circular path about some fixed point at the same time, in the same direction and at the same angle. Common angular movements in sport include rotation around the high bar in gymnastics, bowling a cricket ball or the leg action in the eggbeater kick performed by water polo players.
Sports movements are most commonly referred to as general motion and reflect a combination of both linear and angular motion.

12. Velocity and speed
Velocity measures the displacement of the body and is divided by the time taken to get from point A to point B. In everyday discussion, many people use the words ‘speed’ and ‘velocity’ interchangeably, but frequently they are not the same.
Speed describes only the magnitude of the speed of the body (that is, how quickly the body is moving), whereas velocity describes both magnitude and direction. Speed and velocity are equal only if movement occurs in a straight line. Thus, the speed and the velocity of a cricket batter running one run will be the same. However, if the batter runs two or more runs, the speed and velocity will differ quite markedly, because the displacement would be zero.
One way to solve this problem is by finding the instantaneous speed and velocity of the body. This is done by measuring the average speed and velocity of the body over a short distance. In this case, the instantaneous speed and velocity of the body are equal. In sports, it is usually the velocity of the body at a particular instant that has the greatest effect on the outcome.

13. Velocity and speed

14. Acceleration
Athletes need to be able to increase and decrease velocity rapidly. A rugby league player carrying the ball needs to build up as much velocity as possible to make it difficult to be tackled. A soft baller stealing a base needs to be able to build up velocity before the fielders can react. The soft baller needs to sprint to the base, but then slowdown in order to avoid over-running the base.
These are examples of linear acceleration and linear deceleration, which are a requirement for most team sports and short-distance sprints. The length and frequency of an individual’s stride is also believed to affect acceleration. The legs of a faster runner will have greater angular velocity.
In general, a combination of long stride and high frequency indicates a fast runner. A stride is the distance between one foot striking the ground and when it next strikes the ground; that is, two steps. There are also some slight differences in posture and movement patterns of athletes competing in events of various lengths.

15. Acceleration

16. Activity/task Velocity and acceleration
Equipment
• Measured 100-metre straight line with a cone at each 10-metre interval
• 10 stopwatches
Procedure
1 Place a person with a stopwatch at each cone (10-metre interval).
2 On ‘Go’, everyone starts the stopwatches, and stops them at the moment that the sprinter runs past their cone.
Start____▲____▲____▲____▲____▲____▲____▲____▲____▲____Finish m
Figure 6.4 Set-up for the practical application workshop above

17. Example Usain Bolt’s world record 100m 9.58 seconds
Distance
Time
Velocity
Acceleration
10 metres
 1.88 seconds
 5.32 metres/second
2.83 metres/second²
20 metres
 1.00 seconds
 10.00 metres/second
 4.68 metres/second²
30 metres
 0.92 seconds
 10.87 metres/second
 0.95 metres/second²
40 metres
 0.84 seconds
 11.90 metres/second
 1.23 metres/second²
50 metres
 0.83 seconds
 12.05 metres/second
 0.17 metres/second²
60 metres
 0.82 seconds
 12.20 metres/second
 0.18 metres/second²
70 metres
 0.81 seconds
 12.35 metres/second
 0.19 metres/second²
80 metres
 -0.18 metres/second²
90 metres
 0.00 metres/second²
100 metres
 -0.35 metres/second²
TOTAL
9.58 seconds

18. 1 Graph the results for velocity and acceleration
1 Graph the results for velocity and acceleration. Example Usain Bolt’s world record 100m 9.58 seconds

19. Questions 2 Identify the point at which the sprinter had the:
a greatest velocity? Why do you think this occurred?
b least velocity? Why do you think this occurred?
c greatest acceleration? Why do you think this occurred?
d greatest deceleration? Why do you think this occurred?
3 Discuss the variations in the sprinter’s velocity and acceleration over the 100 metres.
4 Explain the effect these variations could have on the sprinter’s overall performance in a 100-metre sprint race.