ESS2003 Kinesiology and Biomechanics II
Laboratory Session 3
Biomechanical Analysis of Sports Performance
Dr Sharon Dixon
Purpose
To provide students with practical experience of analysing a sports skills using video data.
Aims
1. To use kinematic data to compare kicking performance with the right and left foot.
2. To identify the contribution of different anatomical joints to performance of a tennis serve.
Comparison of Right and Left Footed Kicking
1. Accessing the video file in Hu-m-an.
- Double click the ‘Hu-m-an’ icon on desktop
- File – ‘load trial’.
In ‘Directories/Path’ double click left mouse button on:
‘[-e-]’- progr~1 – studio~1 – captur~1
The video files will be displayed in the left hand box.
Double-click the left mouse button on Left1s~1.avi
2. View the video sequence
In VIDEO-MODEL CONTROL window
- play the video sequence
- slow video playback speed by reducing ‘Speed’ to ‘1’
- experiment with using the video controls
3. Select model for digitising
- Edit – Trial Set Up
Under ‘List of Trial Set Up Titles’ - Select ‘5 Pt. Lower Limb & Ball’
- Load – Yes – Exit
4. Select frames for digitising
In VIDEO-MODEL CONTROL window
- use single frame forwards and backwards to identify the frame where movement begins
- enter this frame number as the ‘Start’ frame at the top of the window.
- Utilities – Set New Trial Subsequence (Yes)
5. Set scaling and digitise the kicking sequence
- Options – Digitise
DIGITISE window will be active
- Use single frame forwards and backwards to identify a frame where both ends of the metre rule
(on the back wall) are clearly visible.
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-
select ‘Scale’
Click ‘OK’,
Click ‘OK’,
under Real Length input 1.0
under Length Units select ‘metres’
digitise (click with left mouse button) the ends of the metre rule
select ‘Apply New Scale’
Return to frame 0
using the left mouse button, select body landmarks as specified in the DIGITISE window
 hip, knee, ankle, heel, ball of foot, ball
click left mouse button to advance to the next frame
if an error is made, click ‘re-digitise this frame’ to redigitise the whole frame
Each member of the group should take turns digitising.
When all frames have been digitised, close the DIGITISE window by clicking ‘exit’.
6. View the model
Using VIDEO-MODEL CONTROL window
- play the sequence to view the video and the model simultaneously
- select (tick) +Model
- view the sequence again
7. Marking ball contact frame
Edit – Trial Setup
Under ‘Subject – Trial Data’ click ‘Build/Edit’
Add
Name the point as ‘ball strike’
Enter the frame number for ball strike (as identified from the video).
Tick the Activate box.
Exit
Exit Trial Setup
8. Calculate segmental angles during kick
Calculate - Absolute angles
Select Thigh (wrt the Hip)
 Calculate
Calculate Absolute Angles
Select Shank (wrt the Knee)
 Calculate
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Draw a stick figure showing the thigh and shank angles as defined in your model:
Figure 1 – Lower extremity segmental angles.
9. Calculate Angular Velocities
Calculate – Velocity
Thigh (wrt the Hip) velocity – Calculate
Calculate – Velocity
Shank (wrt the Knee) velocity – Calculate
In GRAPH DATA CONTROL window
Select Thigh (wrt the Hip) velocity
Select Shank (wrt the Knee) velocity
Graph the angular velocities in Figure 2 and identify the peak angular velocity values (Table 1).
Remember that the velocities for the left foot kick will be reversed, i.e. the positive values are
negative and negative values are positive.
Angular
velocity
(degrees/s)
Frame number
Figure 2 – Thigh and shank angular velocities during kicking.
Include a vertical line in Figure 2 to indicate the point of ball contact.
Complete Table 1.
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Table 1 – Maximum segmental angular velocities in kicking
Peak angular velocity
Timing
Velocity
Velocity
Number of frames
(degrees/s)
(radians/s)
prior to ball contact
Thigh (left)
Shank (left)
Thigh (right)
Shank (right)
10. Calculate linear velocities
Calculate – Velocity
Ball – Resultant Speed – Calculate
Calculate – Velocity
Hip – X Velocity – Calculate
Calculate – Velocity
Knee – X Velocity – Calculate
Calculate – Velocity
Ankle – X Velocity – Calculate
Complete Table 2.
Table 2 – Maximum linear velocities during kicking.
Point
Left foot*
Right foot
Linear
Timing (frames
Linear
Timing (frames
velocity (m/s) prior to contact) velocity (m/s)
prior to contact)
Ball
Hip
Knee
Ankle
*When calculating these values for the left foot kick select the maximum negative values (the
lowest points on the graph) but ignore the sign ( – ).
11. Graph of linear velocities
Graph the linear velocities and complete Figure 3 for the ball, hip, knee and ankle.
Linear
velocity (m/s)
Frame number
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Figure 3 – Linear velocities for the ball, hip, knee and ankle.
Repeat the above procedures for the kick with either Right1~1.avi or Right2~1.avi (use the same
number as you did for the left leg digitisation and complete Table 1 and Table 2.
Questions
1. Describe qualitatively the segmental contributions to a maximal soccer kick.
2. How do the ball speeds compare for the left and right-footed kicks?
3. What are the main differences in kinematics (linear and angular velocities) between the right
and left kicks?
4. Suggest reasons for any observed differences between the right and left.
5. How does the data for the subject you analysed compare with that published in the literature?
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Kinematic Analysis of a Tennis Serve
1. Accessing the video file in Hu-m-an.
- Double click the ‘Hu-m-an’ icon on desktop
- File – ‘load trial’.
In ‘Directories/Path’ double click left mouse button on:
‘[-e-]’- progr~1 – studio~1 – captur~1
The video files will be displayed in the left hand box. Double-click the left mouse button on
‘tennis.avi’.
2. View the video sequence
In VIDEO-MODEL CONTROL window
- play the video sequence
- slow video playback speed by reducing ‘Speed’ to ‘1’
- experiment with using the video controls
3. Select model for digitising
- Edit – Trial Set Up
Under ‘List of Trial Set Up Titles’ - Select ‘11 Pt. Symmetric’
- Load – Yes – Exit
4. Select frames for digitising
In VIDEO-MODEL CONTROL window
- use single frame forwards and backwards to identify the frame where movement ends
- enter this frame number as the ‘End’ frame at the top of the window.
- Utilities – Set New Trial Subsequence (Yes)
5. Digitise the serve sequence
- Options – Digitise
DIGITISE window will be active
Digitise the right side of the body.
-
using the left mouse button, select body landmarks as specified in the DIGITISE window
 head, wrist, elbow, shoulder, hip, knee, ankle, toe, tip of toe, ball, heel
click left mouse button to advance to the next frame
if an error is made, click ‘re-digitise this frame’ to redigitise the whole frame
Each member of the group should take turns digitising.
When all frames have been digitised, close the DIGITISE window.
6. View the model
Using VIDEO-MODEL CONTROL window
- play the sequence to view the video and the model simultaneously
- select (tick) +Model
- view the sequence again
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7. Marking ball contact frame
Edit – Trial Setup
Subject – Trial Data
Add
Name the point as ‘ball strike’
Enter the frame number for ball strike (as identified from the video).
Tick the Activate box.
Exit
Exit Trial Setup
8. Calculate joint angles during serve
Calculate - Relative angles
Select Hip angle
 Calculate
In GRAPH DATA CONTROL window
Select Hip angle
Calculate Relative Angles
Select Knee angle
 Calculate
In GRAPH DATA CONTROL window
Click ‘Clear/Reset’
Select ‘Knee angle’
Calculate Relative Angles
Select Shoulder angle
 Calculate
In GRAPH DATA CONTROL window
Click ‘Clear/Reset’
Select ‘Shoulder angle’
Calculate Relative Angles
Select Elbow angle
 Calculate
In GRAPH DATA CONTROL window
Click ‘Clear/Reset’
Select ‘Elbow angle’
Identify the peak flexion angles during the serve by clicking on the appropriate points of the graph.
Identify the time of peak flexion angle relative to the point of ball contact. Input results in Table 3.
*Peak flexion angles for the HIP, SHOULDER, and KNEE can be calculated by selecting the
maximum point on the graph and taking it away from 360° (360° - ).
ELBOW peak flexion is the nearest point on the graph to 0°.
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Table 3 – Maximum joint flexion and timing during tennis serve
Angle (degrees)
Timing
(frames prior to
ball contact)
Hip
Knee
Ankle
Draw a stick figure showing the joint angles as defined in your model:
Figure 4 – Lower extremity joint angles in the tennis serve
9. Calculate Angular Velocities
Calculate – Velocity
Hip angle – Calculate
Graph the angular velocity and identify the peak angular velocity.
When does this occur relative to ball contact?
Repeat for the knee, shoulder and elbow angular velocities, and complete Table 4.
*Maximum joint angular velocities are the minimum points on the graph during the 10
frames preceeding ball contact. These negative values are positive.
Table 4 – Maximum joint angular velocities in tennis serve.
Maximum angular velocity
Velocity
Velocity
Timing (frames prior to
(degrees/s)
(radians/s)
ball contact)
Hip
Knee
Shoulder
Elbow
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Questions
1. In what order do the maximum flexion angles occur?
2. In what order do the peak angular velocities occur?
3. Compare what you found in the tennis serve with your findings in the soccer kick. Identify
similarities and differences, and their significance.
4. What difficulties were there in digitising the tennis serve sequence? Suggest how these may be
overcome.
Additional Reading
Lees, A. and Nolan, L. (1998). The biomechanics of soccer: A review. Journal of Sports Sciences
16, 211-234.
Dorge, H.C., Bull Andersen, T., Sorensen, H. and Simonsen, E.B. (2002). Biomechanical
differences in soccer kicking with the preferred and non-preferred leg. Journal of Sports Sciences
20, 293-299.
McLean, B.D. and Tumilty, D. McA. (1993). Left-right asymmetry in two types of soccer kick.
British Journal of Sports Medicine 27, 260-262.
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Elliott, B.C., Marshall, R.N. and Noffal, G.J. (1995). Contributions to upper limb segment rotations
during the power serve in tennis. Journal of Applied Biomechanics 11, 433-442.
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