Gait Analysis of Dressage Performance (To be presented by Dr. Hilary Clayton at the CESMAS Equine Sports Medicine Conference, Córdova, Spain, April 23-28, 1998 )    Contents: Introduction Definitions The Walk The Trot The Passage and Piaffe The Canter References Introduction In dressage competitions the experience and ‘eye’ of the judge determines the scores that are awarded to the individual competitors and their placings in the competition. Analysis of video tapes is a method of measuring the horses’ motion patterns (kinematics) and thus quantifying what the judge sees. Of course, video analysis is able to discern many aspects of gait that are not perceived by the judge due to the poor temporal resolution of the human eye. However, the findings are useful for determining exactly how the horses perform the gaits and movements of dressage. This paper will discuss the results of recent kinematic studies of dressage horses.   Definitions Before proceeding it is necessary to define some of the terms that will be used throughout this paper. A gait is distinguished by the sequence and timing of the footfalls, which is repeated in a cyclic manner. A single unit is a stride. The stride starts and ends at the same point in the cycle of limb movements. Tempo (or stride rate) is the rate of repetition of the strides. It is usually measured in strides per minute. Dressage horses are supposed to maintain the same tempo (stride rate) during the transitions between the collected, working, medium and extended gait types. In other words, they should change stride length independent of stride rate. Rhythm describes the timing of the footfalls within the stride. The support sequence is the sequence of limb combinations that support the body weight during a stride.   The Walk The walk is a 4-beat gait in which the sequence of footfalls is RH, RF, LH and LF. This type of footfall sequence, in which the hind footfall is followed by the fore footfall on the same side, is called a lateral sequence. The footfalls at the walk should be evenly spaced in time, giving a regular, 4-beat rhythm. The limb support sequences alternate between bipedal supports (2 limbs in contact with the ground) and tripedal supports (3 limbs in contact with the ground). The bipedal supports always consist of a fore limb and a hind limb, which may be a diagonal or a lateral pair. The tripedal supports may be 2 hind and 1 fore limb or 2 fore and 1 hind limb. There is no period of suspension in the walk, which makes it an easy gait for the rider to sit. The FEI recognizes 4 types of walk: collected, medium, extended and free. The free walk is only performed in lower levels of competition. The velocity, tempo and stride length of the collected, medium and extended walks have been measured and compared in a group of national level FEI horses (Clayton 1995).     Collected Walk  Medium Walk  Extended Walk Velocity (m/s)  1.4a 1.7b 1.8b Stride Length (m)  1.57a 1.87b 1.93b Tempo (strides/min)  52a 55a,b 56b Lateral Distance (cm)  158a 167a 166a Tracking Distance (cm) -7a 19b 27b Different superscripts indicate values that differ significantly, p<0.05   Velocity and stride length were significantly lower in the collected walk than in the medium and extended walks. The tempo of the collected walk was significantly slower than that of the extended walk. Most of the change in speed was result of alterations in stride length. In the walk, stride length can be expressed as the sum of the lateral distance (distance between the hind hoof and the next placement of the fore hoof) plus the tracking distance (distance between the fore hoof and the next placement of the hind hoof). The increase in stride length at the walk was almost entirely due to an increase in tracking distance. In other words, the horses showed more over-tracking in the medium and extended walks. Dressage horses are required to maintain a regular, 4-beat rhythm in the walk, but only a minority of the horses studied have achieved this in the collected, medium and extended walks. Many dressage horses walk with lateral couplets, which means there is a shorter time between footfalls of the hind hoof and the lateral front hoof than between the front hoof and the diagonal hind hoof. This type of rhythm is sometimes referred to as ‘pacing’ in the walk. A few dressage horses have a walk rhythm in which the time between footfalls of the fore hoof and the diagonal hind hoof is shorter than the interval between footfalls of the hind hoof and the lateral fore hoof. Some horses have a more regular rhythm in the collected walk; others have a more regular rhythm in the extended walk. The difference between a regular rhythm, lateral couplets and diagonal couplets is illustrated in figure 1.     REGULAR   RHYTHM: RH ------ RF ------ LH ------ LF ------ RH LATERAL   COUPLETS: RH ---- RF -------- LH ---- LF -------- RH DIAGONAL   COUPLETS: RH -------- RF ---- LH -------- LF ---- RH LEFT WALK   PIROUETTE: RH ------ RF --- LH --------- LF ------ RH Figure 1: Timing of footfalls in the walk with regular rhythm, lateral couplets and diagonal couplets. The rhythm of the walk strides is compared with that of a walk pirouette to the left. The demi pirouette, performed in collected walk, is a half circle in which the horse moves around the inside hind limb, which acts as a pivot. However, the inside hind hoof continues to step in the normal rhythm of the walk. The outside fore limb passes and crosses in front of the inside fore limb. A study of horses competing in the Grand Prix test at the Atlanta Olympics showed that the majority of horses completed the demi pirouette in 3 strides, the remaining horses used 4 strides. None of the horses maintained a regular 4-beat rhythm. Instead, the inside hind footfall occurred relatively early. Consequently, the time between footfalls of the outside fore and inside hind was short, while the time between footfalls of the inside hind and inside fore was long. The typical rhythm for a walk pirouette stride is shown in the diagram.   The Trot The trot is a 2-beat gait in which the diagonal pairs of limbs move synchronously, and the footfalls are evenly spaced in time. The diagonal limb support phases are separated by periods of suspension. Therefore, each stride has 2 diagonal support phases and 2 suspensions. Slow motion analysis has shown that ground contact and lift off of the diagonal fore and hind limbs does not always occur at exactly the same moment. The interval between the fore and hind contacts is known as the advanced placement. The value is positive if the hind limb contacts the ground before the diagonal fore limb, zero if the diagonal pair contact the ground at exactly the same moment, and negative if the hind limb contacts the ground after the fore limb. In dressage horses, a positive diagonal advanced placement (figure 2) is considered to be a desirable characteristic (Holmström 1995). It occurs in horses that travel with an elevated forehand.  Figure 2:  Rembrant shows a high positive diagonal advanced placement in the collected trot  Four types of trot are performed. In order of increasing speed these are: collected, working, medium and extended. The velocity, stride length and tempo of the different types of trot have been measured (Clayton 1994).     Collected Trot Working Trot  Medium Trot  Extended Trot  Velocity (m/s)  3.20a 3.61b 4.47c 4.93d Stride Length (m)  2.50a 2.73b 3.26c 3.55d Tempo (strides/min)  77a 79a,b 82a,b 83b Diagonal Distance (cm)  132a 132a,b 136a,b 137b Tracking Distance (cm)  -7a 4b 27c 39d Suspension (ms)  16a 17a 32b 37b Different superscripts indicate values that differ significantly, p < 0.05   The velocity and stride length are significantly different between each type of trot. The tempo is significantly slower in the collected than in the extended trot. This shows that that there is a tendency for the strides at extended trot to be slightly faster than those at the collected trot. The difference is small enough that it may not be perceptible to a judge. Changes in stride length at the trot depend on alterations in the diagonal distance and the tracking distance. The diagonal distance increases slightly from working to medium trot, probably as a consequence of the lengthening of the horse’s frame. However, most of the increase in stride length is a result of greater over-tracking, which represents the distance covered during the suspension. The best way to increase the over-tracking, and therefore the stride length, is to prolong the suspension. This is achieved by pushing off into the suspension with a higher vertical velocity, so it takes longer for gravity to overcome the upward motion and return the horse to the ground. Some horses naturally have more ‘lift’ than others, but the upward propulsive power can be improved by working on an incline or by trotting over raised rails.   The Passage and Piaffe Like the trot, in passage and piaffe the diagonal limb pairs move more or less in synchrony. A study of horses competing in the Barcelona Olympics compared the velocity, stride length and tempo of the collected trot, passage and piaffe.   Collected Trot Passage  Piaffe Velocity (m/s)  3.3a 1.6b 0.2c Stride Length (m)  2.50a 1.75b 0.20c Tempo (strides/min)  71a 55b 55b Different superscripts indicate values that differ significantly, p < 0.05   Passage and piaffe have the same tempo, but this is considerably slower than that of the collected trot. The stride length and velocity are significantly reduced from collected trot to passage and from passage to piaffe (Clayton 1997). Passage shows many similarities with the trot. It has 2, well-defined suspensions in every stride (figure 2), and an exaggerated positive diagonal advanced placement (hind hoof contacts the ground before the diagonal fore hoof). The majestic appearance of the passage is due to the fact that the limbs pause momentarily in their most elevated position.   Figure 3: The passage shows an large positive diagonal advanced placement (left), a moment in which the limbs are held in their most elevated position during the swing phase (centre) and a period of suspension (right). Piaffe differs in several respects from the collected trot and the passage. The most important of these differences is the absence of a suspension (airborne) phase in piaffe. There is always at least one hoof in contact with the ground (figure 4). Therefore, piaffe is a stepping gait, rather than a leaping gait. However, the amount of overlap between successive diagonal stance phases is shorter in the better quality piaffe. As in the passage, the limbs pause momentarily at their most elevated position in the piaffe. Figure 4: Piaffe sequence showing the stepping from one diagonal pair to the other (3 left pictures) and the moment in which the limbs are suspended at the highest position during the swing phase (right).   The Canter The canter differs from the other gaits of dressage horses in that it is an asymmetrical gait. Consequently, it has a leading and a trailing limb. The leading limbs are normally on the same side of the body in the fore and hind limbs. Four types of canter are performed in competition: collected, medium, working and extended. The velocities, stride lengths and tempos of the 4 types of canter are:   Collected Canter Working Canter  Medium Canter  Extended Canter  Velocity (m/s)  3.27a 3.91b 4.90c 5.97d Stride Length (m)  2.00a,b,c 2.35a,d,e 2.94b,d,f 3.47c,e,f Tempo (strides/min)  99a 99a 101a 105a Suspension (ms)  0a,b 5c,d 54a,c 87b,d Different superscripts indicate values that differ significantly, p < 0.05   The velocity is significantly different between each type of canter, but the tempo stays the same (Clayton 1994). Changes in stride length are mostly a result of alterations in stride length, which are the result of an increase in the distance covered during the suspension, so the ability to project the body upward into the suspension is an important determinant of stride length. There are smaller increases in the distances between the 2 hind limbs and in the distance between the 2 fore limbs. The canter has a 3-beat rhythm initiated by the trailing hind limb, followed by the leading hind limb and trailing fore limb which move in synchrony, and finally the leading fore limb. There is then a longer interval before the next stride is initiated, which includes the airborne time during the suspension. The rhythm differs between the collected and extended canters. In collected canter, the 3 footfalls are more separated and the suspension is short. In extended canter the 3 footfalls are more closely grouped in time, while the interval between strides (during which the horse is in the suspension) becomes longer.   In the canter pirouette, horses are supposed to maintain the tempo and rhythm of the collected canter strides. However, a study of horses competing in the individual medal finals at the Barcelona Olympics showed that neither the tempo nor the rhythm of the collected canter strides was maintained in the canter pirouettes (Burns and Clayton 1997). The tempo was significantly slower in the pirouettes (68 strides/min) than in the collected canter strides (95 strides/min). The footfalls of the diagonal limb pair were dissociated in the pirouette strides giving them a distinct 4 beat rhythm, in contrast to the 3-beat rhythm of the canter strides. Also, there was no period of suspension between successive strides of the pirouettes. The stance duration of the inside hind limb was prolonged, which was interpreted as a means of maintaining the horse’s balance in the absence of forward movement.   References 1. Burns, T.E. and Clayton, H.M. 1997. Comparison of the temporal kinematics of the canter pirouette and collected canter. Equine Veterinary Journal Supplement 23, 58-61 2. Clayton, H.M. 1997. Classification of collected trot, passage and piaffe using stance phase temporal variables. Equine Veterinary Journal Supplement 23, 54-57. 3. Clayton, H.M.  1995. Comparison of the stride kinematics of the collected, medium, and extended walks in horses. American Journal of Veterinary Research 56, 849-852. 4. Clayton, H.M. 1994. Comparison of the stride kinematics of the collected, working, medium, and extended trot. Equine Veterinary Journal 26, 230-234. 5. Clayton, H.M. 1994. Comparison of the collected, working, medium, and extended canters. Equine Veterinary Journal Supplement 17, 16-19. 6. Holmström M, Fredricson I, Drevemo S. (1994) Biokinematic analysis of the Swedish Warmblood riding horses trot.  Equine vet. J. 26, 235-240. 7. Holmström M. Fredricson I. Drevemo S. (1995) Biokinematic effects of collection on the trotting gaits in the elite dressage horse.  Equine vet. J. 27, 281-287.