Knowledge Base

Stand Index Calculation Notes

• Stand Index is only calculated when Stand consists of at least 5 frames and there are at least 3 data points between t(Max area) and the 90th percentile.
• Stand Index is not calculated when two stances were combined and the Max Contact area was in the first stance.
• If the 90th percentile of the time interval does not correspond to a video frame, the software interpolates the Print area between the two video frames that include that time.

Paw Contact Parameters

Max Contact At (s)

Max Contact At (s) is the time in seconds since the start of the run that a paw makes maximum contact with the glass plate. It can be regarded as the point at which the braking phase turns into the propulsion phase during Stand.

Max Contact At (%)

Max Contact At (%) is Max Contact At (s) relative to Stand of a paw. The formula is:

Max Contact At (%) = ((Max Contact At (s) − Initial Contact) / Stand) × 100

Max Contact At (%) is used in research on spinal cord injury. For example, Hamers et al. (2001) found an increase in Max Contact At (%) for both front and hind paws in rats. This increase was more marked following a contusion injury compared to a transection injury.

Max Contact Area

Max Contact Area is the maximum area of a paw that comes into contact with the glass plate. In other words, it is the Print Area at Max Contact At (s).

Max Contact Max Intensity

This is the maximum intensity at the time of maximum contact of a paw. Intensity ranges from 0 to 255. The intensity of a print depends on the degree of contact between a paw and the glass plate and increases with increasing weight. Therefore, Intensity is a measure of weight put on the glass plate. The parameter is extracted from the print at maximum contact by finding the pixels of highest intensity.

The Intensity parameter is used to assess the effects of neuropathic pain, including mechanical allodynia (Vrinten and Hamers, 2003). Vrinten and Hamers found that after a chronic constriction injury, which causes neuropathic pain, Intensity was reduced two weeks after surgery and gradually returned to pre-operative values. This change in Intensity showed a high degree of correlation with Von Frey thresholds.

Max Contact Mean Intensity

This is the mean Intensity of a paw print at Max Contact. Intensity ranges from 0 to 255. See also Max Contact Max Intensity.

X Position

X is the position of the center of the paw print at Max Contact in the horizontal (walking) direction. X is the distance in the Distance Unit from the left side of the walkway to the center of the print.

Y Position

Y is the position of the center of the paw print at Max Contact in the vertical direction. Y is the distance in the Distance Unit from the top of the walkway to the center of the print.

Print Dimensions

Print Length

Print Length is the length (horizontal direction) of the complete print. It is displayed in the Distance Unit selected in the Preferences. The complete print is the sum of all contacts with the glass plate, as if the animal's paw would have been inked.

Print Width

Print Width is the width (vertical direction) of the complete paw print. It is displayed in the Distance Unit selected in the Preferences.

Print Area

Print Area is the surface area of the complete print. The print area is by definition at least as large as the Max Contact Area. It is displayed in the Distance Unit squared, where Distance Unit can be selected in the Preferences.

Intensity Parameters

Max Intensity At (s)

Max Intensity At (s) is the time in seconds since the start of the run that the maximum Intensity is measured.

Max Intensity At (%)

Max Intensity At (%) is the same as Max Intensity At (s), expressed as a percentage of the duration of the Stance phase (Stand). The formula is:

Max Intensity At (%) = ((Max Intensity At (s) − Initial Contact) / Stand) × 100%

Max Intensity

Max Intensity is the maximum intensity of the complete paw print, which is obtained by summing up the pixels of all the paw prints detected in the stance phase.

Min Intensity

Min Intensity is the minimum intensity of the complete paw print.

Mean Intensity

Mean Intensity is the mean intensity of the complete paw print.

Mean Intensity of the 15 Most Intense Pixels

This is the mean Intensity of the 15 pixels of a paw with the highest intensity.

Swing and Stride Parameters

Swing (s)

Swing (s), or Swing Phase, is the duration in seconds of no contact of a paw with the glass plate.

Swing Speed

Swing Speed is the speed (Distance Unit/second) of the paw during Swing. The formula is:

Swing Speed = Stride Length / Swing

Stride Length

Stride Length is the distance (in Distance Units) between successive placements of the same paw. It is obtained by calculating the beeline distance between the center of the paw print of two consecutive placements of the same paw during Max Contact. It is not the difference in the X-coordinates of the two paw print centers.

Step Cycle (s)

Step Cycle is the time in seconds between two consecutive Initial Contacts of the same paw:

Step Cycle = Stand + Swing

Duty Cycle (%)

Duty Cycle (%) expresses Stand as a percentage of Step Cycle:

Duty Cycle = (Stand / (Stand + Swing)) × 100%

Toe and Paw Measurements

For more information on Toe Spread, Intermediate Toe Spread, Manual Print Length, and Paw Angle, refer to the Manual Measurements section.

Toe Spread

Toe Spread is the distance (in Distance Units) between the center of the first and fifth toe of a hind paw.

Intermediate Toe Spread

Intermediate Toe Spread is the distance (in Distance Units) between the center of the second and fourth toe of a hind paw.

Manual Print Length

Manual Print Length is the distance (in Distance Units) between the center of the third toe and the heel of a paw.

Paw Angle Body Axis

Paw Angle Body Axis is the smallest angle (in degrees) between the Manual Print Length line and the line representing the orientation of the body axis.

Paw Angle Movement Vector

Paw Angle Movement Vector is the smallest angle (in degrees) between the Manual Print Length line and the line representing the direction of movement of the animal's body.