Figure 1. Joint markers in walking (left) and trotting (right). Joint markers are located (from top to bottom) on the hip, knee, ankle, and metatarsal.
The subject in the video was a one year and seven months old male cat. The movement was normal for a cat. The subject was coaxed to walk and trot using two different methods. The walk was encouraged by passing a cat treat through the intended motion area. This caused the cat to follow after the treat in a slow walk. The trot was induced by "flicking" the cat's favorite toy across the taping area, causing the cat to quickly trot across the area.
This project is focusing on the angles of the hip and the knee, relative to each other. The joint markers were small squares of tape placed on the joints of the rear left leg of the cat. The joint markers were placed at the hip, knee, ankle and metatarsal. The distance between the hip and knee is 15.24 cm, 12.7 cm from the knee to the ankle, and 10.16 cm from the ankle to the metatarsal.
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Figure 1. Joint markers in walking (left) and trotting (right). Joint markers are located (from top to bottom) on the hip, knee, ankle, and metatarsal. | |
The recording occurred inside an apartment off campus. A Sony Hi8 video camera, with the corresponding tripod, was used to record motion data at 30 frames per second. The power for the recording was supplied by the battery. Extra lighting was provided by household lamps. The location identifiers were soccer cones located 88 cm apart. The video camera was located 213 cm from the taping area. The backdrop was a plain beige wall. Criteria used to judge the trials were based upon the whether of not the cat moved across the taping area smoothly, directly, and without hesitation. It was judged by the recorders' discretion and knowledge of the cat. Three "good" walks and three "good" trots were acquired. One of each was randomly chosen for analysis. Trials were thrown out when the cat did not proceed in a direct line across the taping area.
The videotaped images were digitized at 30 frames/sec using FusionRecorder on Macintosh computers in the Creation stations at the New Media Center at the University of Michigan. The digital video files were trimmed using MoviePlayer so that the data files contained only the frames between the start and the end of the movements. Adobe Premiere was used to convert the Quicktime movie files into a series of individual frame files in PICT format for use with the Motion Plus software. The hip, knee, ankle, and metatarsal joint markers were digitized using Motion Capture. Joint marker coordinate data were exported in spreadsheet format to Motion Analyze for biomechanical analysis.