Knowledge Base

Data Acquisition

Acquisition Procedure

After snapping a background image of the empty walkway, the user clicks Start Acquisition. CatWalk automatically detects when the animal enters the camera view and begins recording. A run stops automatically when the animal leaves the field of view.

Acquired Runs List

For each run, the following variables are displayed:

• Run number
• Start date and time
• Duration
• Compliance status (with reason if non-compliant)
• Walking direction
• Run average speed
• Run maximum speed variation
• Camera gain
• Green intensity threshold

Acquisition Settings

• Auto-Abort — Runs can be automatically aborted if they exceed a set duration. Runs are always stopped at 60 seconds maximum.
• Discard Options — Separately configure whether auto-aborted runs, user-aborted runs, non-compliant runs, and incomplete prints at walkway borders are discarded automatically.
• Sound Feedback — Auditory beeps (1 = run started, 2 = run stopped, 3 = error) can be enabled or disabled.

Run Classification

Paw Print Classification

• Manual Classification — Users draw boxes around prints and assign labels: Right Front (RF), Left Front (LF), Right Hind (RH), Left Hind (LH), Right Hip (RM), Right Knee (RK), Left Hip (LM), Left Knee (LK), Nose (NO), Abdomen (AB), Tail (TA), Genitalia (GT). Grouping boxes around labeled and unlabeled prints of the same paw speeds up labeling.
• Automatic Footprint Classification (AFC) — Optional add-on module. Uses the body contour of the animal to automatically assign paw labels. AFC works best with a clean glass plate, straight uninterrupted runs, and an animal that contacts the glass only with its paws. Manual pre-labeling of non-paw prints before running AFC is recommended. A minimum Max Intensity threshold can be set to filter noise.
• Green Intensity Threshold (Per Run) — Can be adjusted before classification to fine-tune paw detection without affecting other runs.

Error Correction

• Labeling Errors — Reset and re-assign labels using the Print View or Timing View as guides.
• CatWalk Errors — Detected automatically when the same label is assigned to two paws in the same frame. Listed in the Video section for correction.
• Print Errors — Noise or non-paw body parts included in a paw rectangle can be corrected by removing and re-adding prints.
• Combine Stances — Two sub-divided stances of the same paw can be manually combined.

Classification Views

• Print View — Displays all paw prints in 2D. Available in Normal Color, False Color (intensity gradient green–red), and Colorized modes. Prints can be shown all-at-once or per frame.
• Timing View — Time-based gait diagram. Bars represent stance duration per paw; gaps represent swing. Clicking a bar jumps to the corresponding video frame.
• Numerical Results — Per-print table with initial contact time, stand duration, max contact time and area, max and mean intensity, print length, width and area.

Interactive Footprint Measurements

This optional Interactive Footprint Measurement (IFM) module is used for detailed toe measurements on hind paws to calculate functional nerve recovery indices.

• Toe Spread (TS) — Distance between the centre of the first and fifth toe.
• Intermediate Toe Spread (ITS) — Distance between the centre of the second and fourth toe.
• Manual Print Length (PL) — Distance from the centre of the third toe to the heel.
• Paw Angle Body Axis — Smallest angle between the Print Length line and the body axis.
• Paw Angle Movement Vector — Smallest angle between the Print Length line and the calculated movement direction (linear regression over four consecutive body-contour positions).

Data Selection

Data Segmentation Profiles

A Data Segmentation profile selects the portion of each classified run that meets three criteria: minimum number of consecutive steps, average speed range, and maximum allowed speed variation. Multiple profiles can be created and saved; the default All Data profile includes all classified steps.

• Minimum Number of Consecutive Steps — Recommended ≥ 10 (ensures each paw is placed at least twice, enabling calculation of stride-based parameters).
• Average Speed Range — Set in distance units per second.
• Maximum Allowed Speed Variation — Expressed as percentage deviation from run average speed.
• Options to exclude non-compliant runs and/or partially classified runs.

The Selected Data Overview shows the proportion of animals, runs, and steps selected per group and time point.

Parameter Profiles

Parameter profiles allow selection of specific paws and parameters for display in Run Statistics, Group Statistics, and export files. The default All Parameters profile cannot be edited or deleted.

Temporal - Contact

• Initial Contact At (s) — Time since run start when a paw first contacts the glass plate.
• Stand / Stance (s) — Duration of contact of a paw with the glass plate.
• Stand Index — Rate at which the paw loses contact with the glass plate (negative value; more negative = faster lift). Requires ≥ 5 frames of stance.
• Max Contact At (s) — Time since run start at which the paw reaches maximum contact area (transition from braking to propulsion phase).
• Max Contact At (%) — Max Contact At expressed as a percentage of stance duration.

Spatial - Contact Area and Intensity

• Max Contact Area — Surface area of the paw print at Max Contact At.
• Max Contact Max Intensity — Maximum pixel intensity of the print at Max Contact (range 0–255; proxy for weight-bearing).
• Max Contact Mean Intensity — Mean pixel intensity of the print at Max Contact.
• X Position — Horizontal position of the paw print centre at Max Contact.
• Y Position — Vertical position of the paw print centre at Max Contact.
• Print Length — Length (horizontal / walking direction) of the complete print.
• Print Width — Width (perpendicular to walking direction) of the complete print.
• Print Area — Surface area of the complete print (all stance frames combined; ≥ Max Contact Area).

Temporal - Intensity

• Max Intensity At (s) — Time since run start at which maximum print intensity occurs.
• Max Intensity At (%) — Max Intensity At expressed as a percentage of stance duration.
• Max Intensity — Maximum intensity of the complete paw print across all stance frames.
• Min Intensity — Minimum intensity of the complete paw print.
• Mean Intensity — Mean intensity of the complete paw print.
• Mean Intensity of 15 Most Intense Pixels — Mean intensity of the 15 highest-intensity pixels of the print.

Swing and Stride

• Swing (s) — Duration of no contact with the glass plate between two stances.
• Swing Speed — Speed of the paw during swing (Stride Length / Swing).
• Stride Length — Distance between successive placements of the same paw (centre-to-centre at Max Contact).
• Step Cycle (s) — Time between two consecutive Initial Contacts of the same paw (Stand + Swing).
• Duty Cycle (%) — Stand expressed as a percentage of Step Cycle.

Source: CatWalk XT 11.0 Technical Specifications, Noldus Information Technology