|
|
|
In this column, I want to share the results of a study performed in the McPhail Lab earlier this year by Emma Hodson, a student in the Equine Sciences program at Hartpury College in England. Emma joined us for four months in the fall of 1997 and returned for another two months in the summer of 1998. Her project was to compare the tempo and rhythm of the collected walk, the extended walk and the walk pirouette. In this column we'll focus on the walk pirouette. The videos used to study the walk pirouette were taken at the Atlanta Olympics. Our camera was positioned on the short side of the arena, slightly to the left of A. It provided a good view of the left pirouette in horses that performed the pirouette close to the center line, but those horses that performed the pirouette close to the long side of the arena were not completely within the field of view and so could not be included in the analysis. Eleven horses were studied. The aspects that were of interest in this study were the number of strides taken to complete the half pirouette, and the tempo and rhythm of the footfalls during the strides of the walk pirouette. How Many Strides? Ideally, the half pirouette should be completed in three or four strides. We found that eight of the eleven horses in the study completed the half pirouette in three strides, the other three horses used four strides. Therefore, all the horses fulfilled the requirements in this respect. Tempo and Rhythm The walk pirouette strides should maintain the same tempo and rhythm as those of the collected walk. Our results showed that the collected walk had a tempo of 52 strides per minute. The average tempo of the strides in the half pirouette was 50 strides per minute. However, averages are sometimes misleading and if we look at each stride individually we see a difference between the early strides, which actually maintained the same tempo as the collected walk, and the final stride, which had a much slower tempo of 46 strides per minute. In other words, the tempo was maintained until the transitional stride from pirouette to collected walk, when the tempo was noticeably slower. So the challenge for the rider is to keep up the tempo during this transition. The fact that the pirouette has no forward movement presents the horse with a challenge in staying balanced while lifting and replacing its hooves on the ground. In general, the greater the number of hooves that are in contact with the ground at any one time, the more stable and better balanced the horse is. The collected walk has periods when the horse is supported by three legs alternating with periods of support by two legs. In the walk pirouette the periods of support by three legs are prolonged at the expense of the periods of support by two legs as a way of compensating for the lack of forward movement. Some horses even show periods when all four hooves are in contact with the ground simultaneously. Similar to the canter pirouette, the leg that is most useful for helping the horse to improve its balance in the walk pirouette is the inside hind. Consequently, the inside hind hoof has a longer period of ground contact than in the collected walk strides. It is lifted from the ground briefly in each stride and quickly replaced in almost the same hoof print. This rapid lifting and replacement of the inside hind causes the rhythm of the footfalls to change. In the horses studied, only one horse stuck to the ground with the inside hind during a single stride. Ideally the footfalls of the walk are evenly spaced in time to give a regular four-beat rhythm as shown in the diagram. Of course, some horses deviate from this by having a lateral (pacing) or diagonal rhythm, which are also illustrated in the diagram. The walk pirouette strides have their own, distinct rhythm of footfalls that is different from the normal walk stride. To explain how the rhythm of the footfalls changes, let's start the stride with the footfall of the outside hind hoof. The first and second beats of the pirouette strides follow the normal walk rhythm. Then, as a consequence of the inside hind being placed on the ground relatively early in the stride, there is a shorter interval of time between the second and third beats and a longer interval of time between the third and fourth beats of the stride. The illustration shows these time intervals.
 Based on these results, riders should focus on the stepping action of the inside hind leg and the need to keep up the tempo, especially in the final stride when preparing to exit the pirouette.
|