Biomechanics - Intro to Video Data Collection

Question 1

(Knudson 2013) Four task model?

Answer 1

1.) Preparation
2.) Observation
3.) Evaluation and diagnosis
4.) Intervention
(Cyclical)

Question 2

(example for deterministic model) What is the goal of movement for a tennis serve? What will it require?

Answer 2

To gain an advantage by making it difficult for the opponent to return the ball.
Requires a fast serve within the court in different locations.

Question 3

(example for deterministic model) How is the goal of movement for a tennis serve achieved?

Answer 3

Velocity of ball at release.
Speed due to speed of racket (and ball) at contact.
Direction due to angle of racket and ball at contact.

Question 4

Velocity?

Answer 4

Speed and direction.

Question 5

What are critical features related to in relation to the deterministic model?

Answer 5

The technique that is required for the goal of movement to be achieved.

Question 6

How many critical features should there be when analysing a movement?

Answer 6

Between 4-8.

Question 7

(example for critical features) Rationale for grip being a critical feature for a tennis serve?

Answer 7

Determines the path of the racket and forearm/wrist action.

Question 8

(example for critical features) Rationale for toss being a critical feature for a tennis serve?

Answer 8

Determines timing and proper racket path.

Question 9

(example for critical features) Rationale for racket preparation being a critical feature for a tennis serve?

Answer 9

Affects timing and speed of the racket.

Question 10

(example for critical features) Rationale for continuous being a critical feature for a tennis serve?

Answer 10

(Sequential coordination pattern) Determines effective ball trajectory.

Question 11

(example for critical features) Rationale for follow through being a critical feature for a tennis serve?

Answer 11

Maximises racket speed and protects the body.

Question 12

(example for critical features) Rationale for stance being a critical feature for a tennis serve?

Answer 12

Affects balance, accuracy and development of racket speed.

Question 13

How does grip as a critical feature relate to biomechanical principles?

Answer 13

(B5) Is the athlete applying force in the correct direction?

Question 14

How does toss as a critical feature relate to biomechanical principles?

Answer 14

(P1) Flight and projectile motion.

Question 15

How does follow through as a critical feature relate to biomechanical principles?

Answer 15

(F2) Range of motion.

(B4) Is the athlete applying the right amount of muscular force over the appropriate time and distance?

Question 16

How does racket preparation as a critical feature relate to biomechanical principles?

Answer 16

(C4) Stretch-shorten cycle.

(F2) Range of motion.

Question 17

How does continuous as a critical feature relate to biomechanical principles?

Answer 17

(C2) Proximal-to-distal sequence of movements.

(B3) Is the athlete applying force with the muscles in the correct sequence?

Question 18

How does stance as a critical feature relate to biomechanical principles?

Answer 18

(B1) Does the athlete have optimal stability when applying or receiving force?
(F6) Stability.
(B2) Is the athlete using all the muscles that can contribute to the skill?

Question 19

How to write a kinematic description of the movement using the correct anatomical language?

Answer 19

Break the movement down into phases.
Individually consider the joints involved.
Describe the movement identifying the axis and plane (e.g. medial rotation about the longitudinal axis of the humerus).
Not always possible/useful to identify the plane for rapid movements (e.g. tennis serve).

Question 20

What do you need to establish for the critical features and technique points in a movement?

Answer 20

A range of correctness.

Question 21

Impulse formula?

Answer 21

Force x Time

Question 22

(Knudson, 2013) Four task model - Extended observation?

Answer 22

Video footage of what is being observed and using slow mo/replay features/video analysis software e.g. dartfish/quintic.
Can also use multiple observers.

Question 23

Good way to avoid conflict of opinions between the observer and performer?

Answer 23

Watch video footage of performer together.

Question 24

Advantages of video analysis software? (dartfish/quintic)

Answer 24

Ability to display more than one screen at a time.
Use of drawing tools to emphasise coaching points.
Quick calculation of key variables/measurements (i.e. semi-quantitative analysis).
Create presentations and reports.

Question 25

Qualitative analysis using video example?

Answer 25

View video at slow speed/frame by frame.

Question 26

How is qualitative analysis extended to a semi-quantitative level?

Answer 26

By taking simple timings, (e.g. stride frequency) and displacement measures (e.g. joint angles at key times).

Question 27

Quantitative analysis using video examples?

Answer 27

Involves coordinate digitisation/Quintic Digitising).

Question 28

What does coordinate digitisation/Quintic Digitising involve?

Answer 28

Identification of body landmarks to estimate joint axis of rotation.
Coordinates of each point are stored in computer memory via computer mouse.

Question 29

What can coordinate digitisation/Quintic Digitising obtain?

Answer 29

Many more variabes e.g. peak angle velocity.

Question 30

Video recording requirements?

Answer 30

Accurate location of body landmark positions e.g. hip - 2cm superior to and 1cm anterior to the greater trochanter of the femur.
Correct size and clarity of marker.

Question 31

3-4-5 triangle set up for camera?

Answer 31

3m = plane of movement.
4m = adjacent.
5m = hypotenuse.

Question 32

Data collection considerations for obtaining quantitative measurements?

Answer 32

Mount camera on tripod.
3-4-5 triangle.
Zoom in to maximise image of performer.
Focus/no movement of camera.
Include calibration object.
Plain background.

Question 33

What features should the subject have?

Answer 33

Minimal clothing.
Habituation to markers e.g. zinc oxide tape.
Habituation to movement ie.e. a consistent performance.