How The Hoof Meets The Road

We ended part two in this series with a 3-dimenssional movie of the horse with markers. Really what we have at this point is just a movie of the markers. Work now begins by identifying and labeling the 60 or more markers that are attached to the left side of the horse. The number of markers on each bone and the patterns of the markers as they were placed on the horse help identify each marker. Because of the speed of the horse at the running walk some markers may disappear from view of the cameras for a short time. When a marker leaves the camera’s view the marker needs to be labeled again when it reappears in the cameras view. As long as there are at least three markers, from a group of four, in view all the time we can track each bone and use the computer to add the missing marker. Marker identification lets researchers know where each bone begins and ends. Knowing the location of each bone is important so that later the bones can be added to movie. Once the bones are added we can see how the horse moves and what is happening to each bone at any point in time.

The next step in the process is to build a bone model of the horse using computer programs. The model is built by telling the computer program the exact location of each marker in a group. Markers can be either on the left or right side of a bone and they can be either on the top end or bottom end of the bone. Once the location of a marker is entered the bones can be seen in the movie. Because the markers were tracked by more than one camera giving us a 3-D movie we can turn the horse and watch it move from any view point. This means that we can see the horse move as if we were riding it. We can also see the horse move towards us or away from us. This will let the movement of the horse be seen over and over from all positions giving a more complete understanding of what the horse is doing during a running walk. This same process of labeling markers and adding bones is repeated for each horse in the study. By comparing the movement from each horse model an average way of going can be seen. This average describes the running walk. Part 4 in this series will describe how the running walk performed by horses in this study compares with the running walk of horses from 2-dimenssional studies conducted by other researchers.