ESS2003 Kinesiology and Biomechanics II

Laboratory Session 1

Joint Angles in Running

Dr Sharon Dixon

Purpose

To familiarise students with the digitisation of video for calculation of joint angles, and with the changes in sagittal plane joint angles during running.

Aims

To digitise a running sequence.
To calculate knee and ankle angles during running.
To plan data collection in preparation for laboratory session 2.

Procedures

Load the running data file

Double click ‘Hu-m-an’ icon on desktop.

The ‘load trial’ window will appear, (if it does not click [file] – [load trial]).

Under ‘Directories/Path’, double click on the appropriate directory/path until the path under ‘file name’ reads: e:\human\data\run\uphilla\uphilla.avi. Use the ‘up one level’ button to backtrack to the right directory or path.

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

Select model for digitising

-Edit – Trial Set Up

Under ‘List of Trial Set Up Titles’ - Select ‘5 Pt. Lower Limb’

-Load – Yes – Exit

Digitise the running sequence

-Options – Digitise

DIGITISE window will be active

-using the left mouse button, select body landmarks as specified in the DIGITISE window

hip, knee, ankle, heel, ball

-click left mouse button to advance to the next frame

-if an error is made, click ‘re-collect this frame’ to redigitise the whole frame

Each member of the group should take turns digitising a running stride, (right foot strike to right foot strike).

- For each stride, record in Table 1 the frame number at right foot strike, and the frame number at right foot toe off. These frames represent the right foot ground contact phase.

When all frames have been digitised, click ‘Exit’ in the DIGITISE window.

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

Instant calculation of joint angles. The distinction between absolute and relative angles.

Absolute angles.

Options – Instant Calculation

In INSTANT CALCULATION window

Select ‘Absolute Angle’

-digitise hip joint centre

-digitise knee joint centre

Thigh angle to the vertical through the hip joint = ______degrees

Select Absolute Angle

-digitise knee joint centre

-digitise ankle joint centre

Lower leg angle to the vertical = ______degrees

Calculate the foot angle to the vertical through the heel:

Foot angle to the vertical = ______degrees

Select ‘Redisplay’

Relative angles.

Select ‘Relative Angle’

-to calculate the knee angle:

define segment 1

digitise the knee joint centre

digitise the hip joint centre

define segment 2

digitise the knee joint centre

digitise the ankle joint centre

knee angle = ______degrees

-to calculate the ankle angle:

define segment 1

digitise the heel

digitise the ball

define segment 2

digitise the ankle joint centre

digitise the knee joint centre

ankle angle = ______degrees

Click ‘Exit’ to close the INSTANT CALCULATION window.

Calculate joint angles during running

- Calculate - Relative Angles

- Select Knee angle

Calculate

In GRAPH DATA CONTROL window

- Click ‘Clear/Reset’

- Click ‘Run-time Graphs’

- Select ‘Knee angle’

- For each step identify the maximum (extension) and minimum (flexion) knee angle during ground contact, by running through the video frame-by-frame and clicking on the appropriate points of the graph. Input results in Table 1, and sketch the knee angle during ground contact for one stride in Figure 1.

Figure 1 – Knee flexion-extension during ground contact

- Calculate - Relative Angles

- Select Ankle angle

Calculate

In GRAPH DATA CONTROL window

- Click ‘Clear/Reset’

- Select ‘Ankle angle’

- For each step identify the maximum (plantarflexion) and minimum (dorsiflexion) ankle angle during ground contact, by running through the video frame-by-frame and clicking on the appropriate points of the graph. Input results in Table 1, and sketch the ankle angle during ground contact for one stride in Figure 2.

Figure 2 – Ankle plantar-dorsiflexion during ground contact

- Determine the mean, standard deviation, and range of the maximum and minimum knee and ankle angles for the running steps examined. Insert in to Table 1.

Table 1 – Maximum and minimum knee and ankle joint angles during ground contact in running.

Right foot ground contact / Knee angle (degrees) / Ankle angle (degrees)
Step / Frame at
footstrike / Frame at TO / Maximum
(extension) / Minimum
(flexion) / Maximum
(extension) / Minimum
(flexion)
1
2
3
4
5
Maximum
Minimum
Mean
SD

- Draw a stick figure showing the knee and ankle angles as defined in your model.

Figure 3 – Lower extremity joint angles in running

Export angle data

File – Export Graph Data to File

Select :

c:\hu-m-an\temp, and enter a file name (OK)

The exported angle data can now be viewed and manipulated in spreadsheet packages such as Excel.

View data in a spreadsheet

For Excel,

Double-click the Excel icon

File – Open

To open your file in c:\hu-m-an\temp

-Under ‘Files of type:’ select ‘all’ files

-Locate c:\hu-m-an\temp\chosen file name

-Open

The text import wizard will appear.

- Click ‘delimited’

-Next

-Click ‘space’ as the only delimiter

-Next

-Finish

The columns represent the calculated angles in the same order as they appear in the hu-m-an GRAPH DATA CONTROL window.

Produce two graphs in Excel, for the knee and ankle time histories during one ground contact.

Questions.

1. Using Table 1, comment on the variation of the calculated knee and ankle angles throughout the running steps examined.

2. What factors may have influenced the variation in the joint angles observed in question 1?

3. Did you have any problems with digitising the joint centres?

4. Suggest ways in which the digitising process could be made more accurate.

5. Suggest ways in which the digitising process could be made more reliable.

FOR NEXT WEEK.

Plan Data Collection

Choose one person in your group to be a subject for Laboratory 2.

Use your experience in Laboratory Session 1 to plan the collection of running data on the treadmill for the calculation of joint angles in running.

* Bring a floppy disk to your next lab session.

* Read: Dixon, S.J. and Kerwin, D.G. (1999). The influence of heel lift manipulation on sagittal plane joint angles in running. Journal of Applied Biomechanics 15, 139-151.