Influence of rider on lameness in trotting horses

Adaptation strategies of the Icelandic horse with induced forelimb lameness at walk, trot and tölt

BACKGROUND AND OBJECTIVE

Lameness assessment in the gaited Icelandic horse is complex. We aimed to describe their kinematic and temporal adaptation strategies in response to forelimb lameness at walk, trot and tölt.

STUDY DESIGN

In vivo experiment.

METHODS

Ten clinically non-lame Icelandic horses were measured before and after reversible forelimb lameness induction. Upper body and limb kinematics were measured using 11 inertial measurement units mounted on the poll, withers, pelvis (tubera sacrale) and all four limbs and hoofs (Equimoves®, 500 Hz). Horses were measured on a straight line at walk and trot in-hand and at walk, trot and tölt while ridden. Linear mixed models were used to compare baseline and lame conditions (random factor = 'horse'), and results are presented as the difference in estimated marginal means or percentage of change.

RESULTS

Lameness induction significantly (p < 0.05) increased head vertical movement asymmetry at walk (HDmin/HDmaxHAND: 18.8/5.7 mm, HDmin/HDmaxRIDDEN: 9.8/0.3 mm) and trot (HDmin/HDmaxHAND: 18.1/7.8 mm, HDmin/HDmaxRIDDEN: 24.0/9.3 mm). At the tölt, however, HDmin did not change significantly (1.1 mm), but HDmax increased by 11.2 mm (p < 0.05). Furthermore, pelvis vertical movement asymmetry (PDmax) increased by 4.9 mm, sound side dissociation decreased (-8.3%), and sound diagonal dissociation increased (6.5%). Other temporal stride variables were also affected, such as increased stance duration of both forelimbs at walk, tölt and in-hand trot.

MAIN LIMITATIONS

Only one degree of lameness (mild) was induced with an acute lameness model.

CONCLUSIONS

Classical forelimb lameness metrics, such as vertical head and withers movement asymmetry, were less valuable at tölt compared to walk and trot, except for HDmax. Therefore, it is advised to primarily use the walk and trot to detect and quantify forelimb lameness in the Icelandic horse.

Riders' Effects on Horses-Biomechanical Principles with Examples from the Literature

Movements of the horse and rider in equestrian sports are governed by the laws of physics. An understanding of these physical principles is a prerequisite to designing and interpreting biomechanical studies of equestrian sports. This article explains and explores the biomechanical effects between riders and horses, including gravitational and inertial forces, turning effects, and characteristics of rider technique that foster synchronous movement with the horse. Rider symmetry, posture, and balance are discussed in the context of their relationship to rider skill level and their effects on the horse. Evidence is presented to support the feasibility of improving equestrian performance by off-horse testing followed by unmounted therapy and exercises to target the identified deficiencies. The elusive quality of harmony, which is key to a true partnership between riders and horses, is explored and described in biomechanical terms.

Comparison of Asymmetry During Trot In-Hand With Evaluations of Discomfort and Pain in Horses While Exercised

Traditional visual lameness assessment is subjective. Ethograms have been developed for evaluating pain and objective sensors to detect lameness. Heart rate (HR) and heart rate variability (HRV) have been used to evaluate stress and pain. The aim of our study was to compare subjective and behavioral lameness scores, a sensor system measuring movement asymmetry, HR, and HRV. We hypothesized that these measures would show related trends. In 30 horses, an inertial sensor system was used to measure movement asymmetries during trot in-hand. A horse was categorized as sound if each asymmetry was less than 10 mm. We recorded riding to observe lameness and evaluate behavior. Heart rate and RR intervals were measured. Root mean squares of successive RR intervals (RMSSD) were calculated. Five horses were categorized as sound and 25 horses as lame by the inertial sensor system. No significant differences were detected between sound and lame horses in the ethogram, subjective lameness score, HR, and RMSSD. Overall asymmetry, ethogram, and lameness score had no significant correlation with each other, whereas overall asymmetry and ethogram correlated significantly with HR and RMSSD during certain phases of the ridden exercise. The main limitation of our study was the small number of sound horses detected by the inertial sensor system. The association between gait asymmetry and HRV suggests that the more gait asymmetry a horse shows during trot in-hand, the more pain or discomfort it probably experiences when ridden with a higher intensity. The threshold for lameness used by the inertial sensor system may require further evaluation.

The effect of acute equine temporomandibular joint inflammation on response to rein-tension and kinematics

Background

Although the temporomandibular joint (TMJ) is the major contact point between the reins in the riders' hand, the bit in the mouth, and the rest of the horse under saddle, the role of inflammation of this joint on equine locomotion and rein tension is unknown.

Objective

To determine the effect of acute TMJ inflammation on rein-tension and horse movement when horses were long-reined on a treadmill.

Study design

A randomized, controlled, cross-over design.

Methods

Five horses were trained by one clinician to walk and trot on a treadmill wearing long-reining equipment instrumented with a rein-tension device and reflective optical tracking markers. Subjective assessment of horse's dominant side, and movement, were determined without rein-tension (free walk and trot); and with rein-tension (long-reined walk and trot). Continuous rein-force data from both sides were collected over ~60s from each trial. Movement was recorded using a 12-camera optical motion capture system. One randomly assigned TMJ was subsequently injected with lipopolysaccharide and the treadmill tests repeated by investigators blinded to treatment side. A second, identical assessment was performed 10 days later with the opposite TMJ being the target of intervention.

Results

All horses showed reduced rein-tension on the injected (inflamed) side. Increased rein-tension was required on the non-injected side at trot, to maintain them in the correct position on the treadmill post-injection. The only kinematic variable to show any significant change due to rein tension or TMJ inflammation during the walk or trot was an increase in forward head tilt in the presence of rein tension in the trot after injection.

Main limitations

Low number of horses and investigation of response to acute inflammation only.

Conclusion

TMJ inflammation changed, subjectively and objectively, the response to rein-input, but the horses did not become lame.

Application of the Ridden Horse Pain Ethogram to 150 Horses with Musculoskeletal Pain before and after Diagnostic Anaesthesia

The Ridden Horse Pain Ethogram (RHpE) was developed to facilitate the recognition of musculoskeletal pain. The aim of this study was to document changes in RHpE scores before and after diagnostic anaesthesia was performed to alleviate pain ± when the saddle was changed. One hundred and fifty horses underwent ridden exercise as part of an investigation of poor performance. The RHpE was applied before and after the interventions. Fifty-two (34.7%) horses exhibited a bilaterally symmetrical short step length and/or restricted hindlimb impulsion and engagement. Fifty-three (35.3%) horses had episodic lameness; only forty-five (30.0%) horses were continuously lame. The median maximum lameness grade when ridden was 2/8 (interquartile range [IQR]: 0-3; range: 0-4). Fifty-six (37.3%) horses had an ill-fitting saddle, which was considered likely to influence performance. The median RHpE scores after the interventions (2/24 [IQR: 1-3, range: 0-12]) were significantly lower than before the interventions (9/24 [IQR: 8-11, range: 2-15]) (Wilcoxon signed-rank z = 10.6, p < 0.001). There was no correlation between the RHpE score and maximum lameness grade before diagnostic anaesthesia (Spearman's rho = 0.09, p = 0.262). It was concluded that the absence of overt lameness does not preclude primary musculoskeletal pain. Gait quality and performance can be improved by diagnostic anaesthesia, with substantial reductions in RHpE scores.

Evaluation of feedback methods for improved detection of hindlimb lameness in horses among riding instructors and trainers

Lameness, a wellknown issue in sport horses, impedes performance and impairs welfare. Early detection of lameness is essential for horses to receive needed treatment, but detection of hindlimb lameness is challenging. Riding instructors and trainers observe horses in motion in their daily work and could contribute to more efficient lameness detection. In this cross-sectional and prospective study, we evaluated the ability of riding instructors and trainers to assess hindlimb lameness. We also evaluated different feedback methods for improved lameness detection. For the cross-sectional part, n = 64 riding instructors and trainers of varying level and n = 23 high-level trainers were shown 13 videos of trotting horses, lameness degree: 0–3.5 (test 1) and tasked with classifying the horses as sound, left hindlimb lame, or right hindlimb lame. For the prospective part, the riding instructors and trainers of varying levels were randomly allocated to three different groups (a, b, c) and given 14 days of feedback-based, computer-aided training in identifying hindlimb lameness, where they assessed 13 videos (of which three were repeated from test 1) of horses trotting in a straight line. Participants in groups a-c received different feedback after each video (group a: correct answer and re-viewing of video at full and 65% speed; group b: correct answer, re-viewing of video at full and 65% speed, narrator providing explanations; group c: correct answer and re-viewing of video at full speed). After computer-aided training, the participants were again subjected to the video test (test 2). Participants also provided background information regarding level of training etcetera. Effects of participants' background on results were analyzed using analysis of variance, and effects of the different feedback methods were analyzed using generalized estimation equations. On test 1, 44% (group a), 48% (b), 46% (c), and 47% (high-level trainers) of horses were correctly classified. Group a participants significantly improved their test score, both with (p < 0.0001) and without (p = 0.0086) inclusion of repeated videos. For group c, significant improvement was only seen with inclusion of repeated videos (p = 0.041). For group b, no significant improvement was seen (p = 0.51). Although test 2 scores were low, computer-aided training may be useful for improving hindlimb lameness detection.

Upper Body Movement Symmetry in Reining Quarter Horses during Trot In-Hand, on the Lunge and during Ridden Exercise

Veterinary lameness examinations often comprise assessing ridden horses. Quantitative movement symmetry measurements can aid evidence-based decision making. While these are available for ‘English’ style riding, they are not for ‘Western’ style riding. This quantitative observational study quantified movement symmetry in reining Quarter Horses (QHs). Movement symmetry of the head, withers and sacrum (differences between minima, maxima and upward amplitudes) were quantified with inertial sensors in N = 30 medium/high level reining QHs during trot in-hand, on the lunge and ridden by one experienced rider (straight-line/circles) on reining-purpose riding surfaces. Mixed linear models for movement symmetry assessed the effects of ridden exercise and movement direction (fixed factors), stride time (covariate) and horse (random factor): single factors and two-way interactions with Bonferroni correction at p < 0.05. Three withers and pelvic parameters showed marginally more symmetrical movement when ridden (p ≤ 0.044; 1−5 mm differences). Three withers, three sacrum and one head parameter were significantly affected by movement direction (all p ≤ 0.026), five showed increased asymmetry on the inside rein, and two, quantifying vertical displacement maximum difference, showed the opposite. Riding QHs in ‘Western’ style showed small movement symmetry differences. Circular exercise confirmed increases in weight bearing asymmetry on the inside rein and in pushoff asymmetry on the outside rein. This should be further investigated for differentiating between different causes of lameness.

The effect of horseshoes and surfaces on horse and jockey centre of mass displacements at gallop

Horseshoes influence how horses' hooves interact with different ground surfaces, during the impact, loading and push-off phases of a stride cycle. Consequently, they impact on the biomechanics of horses' proximal limb segments and upper body. By implication, different shoe and surface combinations could drive changes in the magnitude and stability of movement patterns in horse-jockey dyads. This study aimed to quantify centre of mass (COM) displacements in horse-jockey dyads galloping on turf and artificial tracks in four shoeing conditions: 1) aluminium; 2) barefoot; 3) GluShu; and 4) steel. Thirteen retired racehorses and two jockeys at the British Racing School were recruited for this intervention study. Tri-axial acceleration data were collected close to the COM for the horse (girth) and jockey (kidney-belt), using iPhones (Apple Inc.) equipped with an iOS app (SensorLog, sample rate = 50 Hz). Shoe-surface combinations were tested in a randomized order and horse-jockey pairings remained constant. Tri-axial acceleration data from gallop runs were filtered using bandpass Butterworth filters with cut-off frequencies of 15 Hz and 1 Hz, then integrated for displacement using Matlab. Peak displacement was assessed in both directions (positive 'maxima', negative 'minima') along the cranio-caudal (CC, positive = forwards), medio-lateral (ML, positive = right) and dorso-ventral (DV, positive = up) axes for all strides with frequency ≥2 Hz (mean = 2.06 Hz). Linear mixed-models determined whether surfaces, shoes or shoe-surface interactions (fixed factors) significantly affected the displacement patterns observed, with day, run and horse-jockey pairs included as random factors; significance was set at p<0.05. Data indicated that surface-type significantly affected peak COM displacements in all directions for the horse (p<0.0005) and for all directions (p≤0.008) but forwards in the jockey. The largest differences were observed in the DV-axis, with an additional 5.7 mm and 2.5 mm of downwards displacement for the horse and jockey, respectively, on the artificial surface. Shoeing condition significantly affected all displacement parameters except ML-axis minima for the horse (p≤0.007), and all displacement parameters for the jockey (p<0.0005). Absolute differences were again largest vertically, with notable similarities amongst displacements from barefoot and aluminium trials compared to GluShu and steel. Shoe-surface interactions affected all but CC-axis minima for the jockey (p≤0.002), but only the ML-axis minima and maxima and DV-axis maxima for the horse (p≤0.008). The results support the idea that hoof-surface interface interventions can significantly affect horse and jockey upper-body displacements. Greater sink of hooves on impact, combined with increased push-off during the propulsive phase, could explain the higher vertical displacements on the artificial track. Variations in distal limb mass associated with shoe-type may drive compensatory COM displacements to minimize the energetic cost of movement. The artificial surface and steel shoes provoked the least CC-axis movement of the jockey, so may promote greatest stability. However, differences between horse and jockey mean displacements indicated DV-axis and CC-axis offsets with compensatory increases and decreases, suggesting the dyad might operate within displacement limits to maintain stability. Further work is needed to relate COM displacements to hoof kinematics and to determine whether there is an optimum configuration of COM displacement to optimise performance and minimise injury.

Differential Rotational Movement of the Thoracolumbosacral Spine in High-Level Dressage Horses Ridden in a Straight Line, in Sitting Trot and Seated Canter Compared to In-Hand Trot

Assessing back dysfunction is a key part of the investigative process of "loss of athletic performance" in the horse and quantitative data may help veterinary decision making. Ranges of motion of differential translational and rotational movement between adjacent inertial measurement units attached to the skin over thoracic vertebrae 5, 13 and 18 (T5, T13, T18) lumbar vertebra 3 (L3) and tuber sacrale (TS) were measured in 10 dressage horses during trot in-hand and ridden in sitting trot/canter. Straight-line motion cycles were analysed using a general linear model (random factor: horse; fixed factor: exercise condition; Bonferroni post hoc correction: p < 0.05). At T5-T13 the differential heading was smaller in sitting trot (p ≤ 0.0001, 5.1° (0.2)) and canter (p ≤ 0.0001, 3.2° (0.2)) compared to trotting in-hand (7.4° (0.4)). Compared to trotting in-hand (3.4° (0.4)) at T18-L3 differential pitch was higher in sitting trot (p ≤ 0.0001, 7.5° (0.3)) and canter (p ≤ 0.0001, 6.3° (0.3)). At L3-TS, differential pitch was increased in canter (6.5° (0.5)) compared to trotting in-hand (p = 0.006, 4.9° (0.6)) and differential heading was higher in sitting trot (4° (0.2)) compared to canter (p = 0.02, 2.9° (0.3)). Compared to in-hand, reduced heading was measured in the cranial-thoracic area and increased in the caudal-thoracic and lumbar area. Pitch increased with ridden exercise from the caudal-thoracic to the sacral area.

Horses Could Perceive Riding Differently Depending on the Way They Express Poor Welfare in the Stable

This study investigated the relationships between four behavioral and postural indicators of a compromised welfare state in loose boxes (stereotypies, aggressive behaviors toward humans, withdrawn posture reflecting unresponsiveness to the environment, and alert posture indicating hypervigilance) and the way horses perceived riding. This perception was inferred using a survey completed by the usual riding instructor and during a standardized riding session (assessment of behaviors and postures, qualitative behavior assessment (QBA) and characterization of the horses' locomotion using an inertial measurement unit). In accordance with ear and tail positions and the QBA, stereotypic and the most hypervigilant horses in loose boxes seemed to experience a more negative affective state during the riding session compared with nonstereotypic and less hypervigilant animals (P < .02 in all cases). Horses which were aggressive toward humans in loose boxes had higher scores regarding the occurrence of discomfort and defensive behaviors on the survey than nonaggressive horses (P = .03). They also presented higher dorsoventral accelerations at a canter during the riding session (P = .03), requiring the rider to increase his spinal movement (P = .005). These results suggest that aggressive horses may be harder to ride than nonaggressive animals. The expression of unresponsiveness to the environment in loose boxes was related to more reluctance to move forward, as assessed in the survey (P = .006). This study suggests that a compromised welfare state in the stable is related to horses having a more negative perception of riding. This perception could vary depending on the expression of poor welfare.

Application of a Ridden Horse Pain Ethogram and Its Relationship with Gait in a Convenience Sample of 60 Riding Horses

A Ridden Horse Pain Ethogram (RHpE) comprising 24 behaviours has been developed to facilitate the identification of musculoskeletal pain. The aim was to further test the RHpE by its application to a convenience sample (n = 60) of sports horses and riding school horses in regular work and assumed by their owners to be working comfortably. All horses performed a purpose-designed dressage-type test of 8.5 min duration in walk, trot and canter, with their normal rider. The RHpE was applied retrospectively to video recordings acquired in a standardised fashion. Seventy-three percent of horses were lame (≤ grade 2/8) on one or more limbs; 47% had gait abnormalities in canter. Ridden Horse Pain Ethogram scores ranged from 3 to 16/24 (median 9); rider skill score ranged from 2.5 to 8/10 (median 4.75). The effect of horse age, breed, sex, work-discipline, epaxial muscle hypertonicity or pain, an ill-fitting saddle, rider skill score, the presence of lameness or gait abnormalities in canter on the RHpE score was assessed using Poisson regression. Two variables were retained in the final multivariable analysis, rider skill score as a continuous variable (p < 0.001), and lameness (p = 0.008). A RHpE score ≥8 was a good indicator of the presence of musculoskeletal pain.

Asymmetries of horses walking and trotting on treadmill with and without rider

BACKGROUND

Left-right movement symmetry is a highly desirable characteristic in sport horses.

OBJECTIVES

This study compared movement symmetry in well-trained dressage horses in unridden and unrestrained position and ridden in a dressage frame, and investigated possible associations between gaits.

STUDY DESIGN

Experimental study.

METHODS

Seven sound, high-level dressage horses were measured at walk and sitting trot on a treadmill at several speeds under two conditions: with and without rider. Left-right differences in stance duration, stance protraction and retraction based on longitudinal hoof positions, ipsilateral limb tracking, minimum and maximum vertical positions of the dorsal spinous processes of the sixth thoracic (T6), third sacral vertebrae (S3) and wing of atlas, and vertical ground reaction forces were calculated and analysed in mixed models.

RESULTS

At walk, five body variables indicated increased asymmetry in the ridden condition compared with unridden condition: forelimb stance duration (unridden/ridden left-right differences 9 vs 13 ms; P = .008), forelimb stance protraction (P = .004), stance retraction (P = .001) and first force peak (P = .003), and hindlimb stance retraction (P = .01). At trot, six body variables were more asymmetrical in the ridden condition: forelimb stance duration (2.5 vs 3.8 ms, P = .004); hindlimb stance protraction (P < .0001) and retraction (P = .01), T6 minimum (4 vs 6 mm, P = .001), T6 maximum (9 vs 11 mm, P = .01) and S3 maximum (6 vs 12 mm, P < .001). Five variables had significant associations between asymmetries at walk and trot, but only three demonstrated a positive slope.

MAIN LIMITATIONS

A limited number of horses and riders were studied. Measurements were performed on a treadmill.

CONCLUSIONS

High-level horses moved slightly more asymmetrically when ridden in a dressage frame than in the unridden condition.

Equestrian and biomechanical perspectives on laterality in the horse

It has been suggested that one of the underlying causes of asymmetrical performance and left/right bias in sound riding horses is laterality originating in the cerebral cortices described in many species. The aim of this paper is to review the published evidence for inherent biomechanical laterality in horses deemed to be clinically sound and relate these findings to descriptions of sidedness in equestrian texts. There are no established criteria to determine if a horse is left or right dominant but the preferred limb has been defined as the forelimb that is more frequently protracted during stance and when grazing. Findings on left-right differences in forelimb hoof shape and front hoof angles have been linked to asymmetric forelimb ground reaction forces. Asymmetries interpreted as motor laterality have been found among foals and unhandled youngsters, and the consistency or extent of asymmetries seems to increase with age. Expressions of laterality also vary with breed, sex, training and handling, stress, and body shape but there are no studies of the possible link between laterality and lameness. In a recent study of a group of seven dressage horses, a movement pattern in many ways similar to descriptions of sidedness in the equestrian literature, e.g. one hind limb being more protracted and placed more laterally than the other, has been documented. The role of innate laterality versus painful conditions, training, human handedness and simply habit remains to be determined. Understanding the biomechanical manifestations of laterality in healthy horses, including individual variation, would yield a potential basis for how laterality should be taken into account in relation to training/riding and rehabilitation of lameness.

Collisional mechanics of the diagonal gaits of horses over a range of speeds

One of the goals of the neuromotor control system is to minimize the cost of locomotion by reducing mechanical energy losses. Collisional mechanics, which studies the redirection of the downwards motion of the center of mass (COM) by ground reaction forces (GRF) generated by the limbs, represents an important source of energy loss. The primary objective of this study was to compare collisional mechanics and the associated mechanical energy losses in horses performing diagonally-synchronized gaits over a range of speeds. It is to be expected that collisional energy losses will be high when the COM velocity vector is closely aligned with the GRF vector. This condition is achieved in piaffe, an artificial gait performed in dressage competitions that has a diagonal limb coordination pattern similar to trot but performed with little or no forward velocity. Therefore, we hypothesized that collisional energy losses would be higher in piaffe than in trot. Synchronized kinematic and GRF data were collected from three highly-trained horses performing piaffe, passage and trot at a range of speeds. Derived variables were vertical excursion and velocity of the trunk COM, fore and hind limb compression expressed as percentage reduction of standing limb lengths, range of limb pro-retraction, GRF vector magnitude and vector angle, collision angle (Φ), and mechanical cost of motion (CoMot_mech). Linear regression was used to investigate the relationship between CoMot_mech and speed for each gait. Partial correlation was used to seek relationships between COM excursion and limb mechanics for each gait. Piaffe, passage and trot were clearly separated on the basis of speed. In all gaits the trunk was high at contact and lift off and descended to its lowest point in midstance following the pattern typical of spring mass mechanics. Mechanical cost was significantly (p < .05) and inversely related to speed in trot and piaffe with the value increasing steeply as speed approached zero due to a near vertical orientation of both the COM velocity vector and the GRF vector. Limb compression during stance was significantly (p < .05) linked to trunk COM vertical excursion in all gaits, with a stronger relationship in the forelimb. Hindlimb compression was, however, large in piaffe where the force magnitudes are notably smaller. The study illustrates the potential value of studying artificial gaits to provide data encompassing the entire range of locomotor capabilities. The results supported the experimental hypothesis by showing a threefold increase in collisional energy losses in piaffe compared with trot. In all gaits, dissociation between diagonal limb contacts and lift offs was thought to be an important strategy in reducing in collisional losses. Piaffe, the most costly gait, has similar characteristics to hopping on the spot. It appears that greater hindlimb compliance and a lower step frequency are important energy conservation strategies for piaffe.

Lameness Evaluation of the Athletic Horse

Lameness examination is commonly performed in the athletic horse. A skilled lameness diagnostician must have keen clinical and observational skills. Evaluation starts with a detailed history and thorough physical examination. Next, gait evaluation in the moving horse is performed. Lame horses have asymmetrical body movement due to unconscious shift of body weight. Recognition of the resultant head nod and pelvic hike is the basis for lameness diagnosis. Lameness identification is enhanced by circling, limb flexions, and riding. Most lame horses do not exhibit pathognomonic gait characteristics, and therefore, diagnostic analgesia is the best way to authenticate underlying sites of pain.

Influence of seating styles on head and pelvic vertical movement symmetry in horses ridden at trot

Detailed knowledge of how a rider’s seating style and riding on a circle influences the movement symmetry of the horse’s head and pelvis may aid rider and trainer in an early recognition of low grade lameness. Such knowledge is also important during both subjective and objective lameness evaluations in the ridden horse in a clinical setting. In this study, inertial sensors were used to assess how different rider seating styles may influence head and pelvic movement symmetry in horses trotting in a straight line and on the circle in both directions. A total of 26 horses were subjected to 15 different conditions at trot: three unridden conditions and 12 ridden conditions where the rider performed three different seating styles (rising trot, sitting trot and two point seat). Rising trot induced systematic changes in movement symmetry of the horses. The most prominent effect was decreased pelvic rise that occurred as the rider was actively rising up in the stirrups, thus creating a downward momentum counteracting the horses push off. This mimics a push off lameness in the hindlimb that is in stance when the rider sits down in the saddle during the rising trot. On the circle, the asymmetries induced by rising trot on the correct diagonal counteracted the circle induced asymmetries, rendering the horse more symmetrical. This finding offers an explanation to the equestrian tradition of rising on the ‘correct diagonal.’ In horses with small pre-existing movement asymmetries, the asymmetry induced by rising trot, as well as the circular track, attenuated or reduced the horse’s baseline asymmetry, depending on the sitting diagonal and direction on the circle. A push off hindlimb lameness would be expected to increase when the rider sits during the lame hindlimb stance whereas an impact hindlimb lameness would be expected to decrease. These findings suggest that the rising trot may be useful for identifying the type of lameness during subjective lameness assessment of hindlimb lameness. This theory needs to be studied further in clinically lame horses.

Head and pelvic movement asymmetries at trot in riding horses in training and perceived as free from lameness by the owner

Recent studies evaluating horses in training and considered free from lameness by their owners have identified a large proportion of horses with motion asymmetries. However the prevalence, type and magnitude of asymmetries when trotting in a straight line or on the lunge have not been investigated. The aim of this study was to objectively investigate the presence of motion asymmetries in riding horses in training by identifying the side and quantifying the degree and type (impact, pushoff) of forelimb and hind limb asymmetries found during straight line trot and on the lunge. In a cross-sectional study, vertical head and pelvic movement symmetry was measured in 222 Warmblood type riding horses, all without perceived performance issues and considered free from lameness by their owners. Body-mounted uni-axial accelerometers were used and differences between maximum and minimum head (HDmax, HDmin) and pelvic (PDmax, PDmin) vertical displacement between left and right forelimb and hind limb stances were calculated during straight line trot and on the lunge. Previously reported symmetry thresholds were used. The thresholds for symmetry were exceeded in 161 horses for at least one variable while trotting in a straight line, HDmin (n = 58, mean 14.3 mm, SD 7.1), HDmax (n = 41, mean 12.7 mm, SD 5.5), PDmax (n = 87, mean 6.5 mm, SD 3.10), PDmin (n = 79, mean 5.7 mm, SD 2.1). Contralateral and ipsilateral concurrent forelimb and hind limb asymmetries were detected in 41 and 49 horses, respectively. There was a linear association between the straight line PDmin values and the values on the lunge with the lame limb to the inside of the circle. A large proportion (72.5%) of horses in training which were perceived as free from lameness by their owner showed movement asymmetries above previously reported asymmetry thresholds during straight line trot. It is not known to what extent these asymmetries are related to pain or to mechanical abnormalities. Therefore, one of the most important questions that must be addressed is how objective asymmetry scores can be translated into pain, orthopedic abnormality, or any type of unsoundness.

Riders’ perception of symmetrical pressure on their ischial tuberosities and rein contact tension whilst sitting on a static object

The horse-rider system is of great interest in understanding the mechanics involved in optimising locomotor function and performance in the ridden horse. Adult riders (n=30) attending a rider conference volunteered to take part in the study. Riders were asked to mimic riding position by positioning themselves symmetrically on their seat bones (ischial tuberosities) sitting on a (Pliance) pressure mat which was placed on a static platform. Riders were also asked to mimic even rein contact using reins with gauges which were attached to a solid wall. When satisfied that they were sitting symmetrically and had an even rein contact, pressure and rein measurements were captured for 5 s and repeated three times. A paired T Test was carried out to determine differences between left and right ischial tuberosities and rein pressures. Using a static model, this study found that the riders had significantly more pressure beneath the left ischial tuberosity (mean ± standard deviation, 3.22±1.43 N/cm2) compared to the right (2.65±1.49 N/cm2) (P=0.04) and no significant differences were observed between left (6.37±2.42 N) and right rein pressure (6.38±2.66 N) (P=0.95). Whilst sitting on a static platform, differences in ischial tuberosity pressure in adult riders were observed despite these riders’ perception that their seat was symmetrically weighted. These differences observed need to be investigated further, dynamically, to determine if there is a similar trend in the ridden situation.

Body lean angle in sound dressage horses in-hand, on the lunge and ridden

Animals can minimise the risk of falling by leaning into a curve. The aims of this study were: (1) to quantify the difference between observed (measured by an inertial measurement unit, IMU) and predicted body lean angle (calculated as a cyclist when turning) in horses; and (2) to compare circles versus straight lines ridden versus in-hand and trot with canter, and investigate the influence of age, rein and ridden work quality in trot (Fédération Equestre Internationale grading scale 1-10) in horses. Thirteen non-lame horses were assessed prospectively in a non-random, cross-sectional survey. The horses were trotted in straight lines, lunged and ridden on both reins. A global positioning system-aided IMU attached to the skin over the tuber sacrale quantified body lean and recorded the velocity and the radius, which were used to calculate predicted lean. Horses ≤ 6 years of age leant more than predicted (mean ± standard deviation 2.9 ± 2.6°) and more than horses ≥ 7 years old (0.4 ± 3°) (P = 0.01). Horses that scored ≥ 7 in ridden work quality leant less than predicted (-1.1 ± 2.7°) and less than horses which scored ≤ 6 in ridden work quality (2.4 ± 1.5°) (P = 0.02). There were no significant differences between trot and canter, either on the lunge or ridden (P = 0.3), or between left and right reins (P = 0.2). Asymmetry of body lean between reins may be abnormal and may be helpful for recognition of lameness.

Introduction to Equine Physical Therapy and Rehabilitation

Physical therapy (physiotherapy, or PT) can be broadly defined as the restoration of movement and function and includes assessment, treatment, and rehabilitation. This review outlines the history, definition, and regulation of PT, followed by the core scientific principles of PT. Because musculoskeletal physiotherapy is the predominant subdiscipline in equine PT, encompassing poor performance, back pain syndromes, other musculoskeletal disorders, and some neuromuscular disorders, the sciences of functional biomechanics, neuromotor control, and the sensorimotor system in the spine, pelvis, and peripheral joints are reviewed. Equine PT also may involve PT assessment and treatment of riders.

Head and pelvic movement asymmetry during lungeing in horses with symmetrical movement on the straight

Reasons for performing study

Lungeing is commonly used as part of standard lameness examinations in horses. Knowledge of how lungeing influences motion symmetry in sound horses is needed.

Objectives

The aim of this study was to objectively evaluate the symmetry of vertical head and pelvic motion during lungeing in a large number of horses with symmetric motion during straight line evaluation.

Study design

Cross‐sectional prospective study.

Methods

A pool of 201 riding horses, all functioning well and considered sound by their owners, were evaluated in trot on a straight line and during lungeing to the left and right. From this pool, horses with symmetric vertical head and pelvic movement during the straight line trot (n = 94) were retained for analysis. Vertical head and pelvic movements were measured with body mounted uniaxial accelerometers. Differences between vertical maximum and minimum head (HDmax, HDmin) and pelvic (PDmax, PDmin) heights between left and right forelimb and hindlimb stances were compared between straight line trot and lungeing in either direction.

Results

Vertical head and pelvic movements during lungeing were more asymmetric than during trot on a straight line. Common asymmetric patterns seen in the head were more upward movement during push‐off of the outside forelimb and less downward movement during impact of the inside limb. Common asymmetric patterns seen in the pelvis were less upward movement during push‐off of the outside hindlimb and less downward movement of the pelvis during impact of the inside hindlimb. Asymmetric patterns in one lunge direction were frequently not the same as in the opposite direction.

Conclusions

Lungeing induces systematic asymmetries in vertical head and pelvic motion patterns in horses that may not be the same in both directions. These asymmetries may mask or mimic fore‐ or hindlimb lameness.

Lungeing on hard and soft surfaces: Movement symmetry of trotting horses considered sound by their owners

REASONS FOR PERFORMING STUDY

Lungeing is often part of the clinical lameness examination. The difference in movement symmetry, which is a commonly employed lameness measure, has not been quantified between surfaces.

OBJECTIVES

To compare head and pelvic movement symmetry between surfaces and reins during lungeing.

STUDY DESIGN

Quantitative gait analysis in 23 horses considered sound by their owners.

METHODS

Twenty-three horses were assessed in-hand and on the lunge on both reins on hard and soft surfaces with inertial sensors. Seven movement symmetry parameters were quantified and used to establish 2 groups, namely symmetrical (n = 9) and forelimb-lame horses (n = 14), based on values from straight-line assessment. Movement symmetry values for left rein measurements were side corrected to allow comparison of the amount of movement symmetry between reins. A mixed model (P<0.05) was used to study effects on movement symmetry of surface (hard/soft) and rein (inside/outside with respect to movement symmetry on the straight).

RESULTS

In forelimb-lame horses, surface and rein were identified as significantly affecting all head movement symmetry measures (rein, all P<0.0001; surface, all P<0.042). In the symmetrical group, no significant influence of surface or rein was identified for head movement symmetry (rein, all P>0.245; surface, all P>0.073). No significant influence of surface or rein was identified for any of the pelvic movement symmetry measures in either group.

CONCLUSIONS

While more symmetrical horses showed a consistent amount of movement symmetry across surfaces/reins, horses objectively quantified as lame on the straight showed decreased movement symmetry during lungeing, in particular with the lame limb on the inside of a hard circle. The variation within group questions straight-line movement symmetry as a sole measure of lameness without quantification of movement symmetry on the lunge, ideally on hard and soft surfaces to evaluate differences between reins and surfaces. In future, thresholds for lungeing need to be determined using simultaneous visual and objective assessment.

Posture, flexibility and grip strength in horse riders

Since the ability to train the horse to be ambidextrous is considered highly desirable, rider asymmetry is recognized as a negative trait. Acquired postural and functional asymmetry can originate from numerous anatomical regions, so it is difficult to suggest if any is developed due to riding. The aim of this study was therefore to assess symmetry of posture, strength and flexibility in a large population of riders and to determine whether typical traits exist due to riding. 127 right handed riders from the UK and USA were categorized according to years riding (in 20 year increments) and their competition level (using affiliated test levels). Leg length, grip strength and spinal posture were measured and recorded by a physiotherapist. Standing and sitting posture and trunk flexibility were measured with 3-D motion capture technology. Right-left differences were explored in relation to years riding and rider competitive experience. Significant anatomical asymmetry was found for the difference in standing acromion process height for a competition level (−0.07±1.50 cm Intro/Prelim; 0.02±1.31 cm Novice; 0.43±1.27 cm Elementary+; p=0.048) and for sitting iliac crest height for years riding (−0.23±1.36 cm Intro/Prelim; 0.01±1.50 cm Novice; 0.86±0.41 cm Elementary+; p=0.021). For functional asymmetry, a significant interaction was found for lateral bending ROM for years riding x competition level (p=0.047). The demands on dressage riders competing at higher levels may predispose these riders to a higher risk of developing asymmetry and potentially chronic back pain rather than improving their symmetry.

The interrelationship of lameness, saddle slip and back shape in the general sports horse population

REASONS FOR PERFORMING STUDY

Saddle slip is usually blamed on saddle fit, crooked riders or horse shape, but may reflect hindlimb lameness. There are no studies of the frequency of occurrence of saddle slip and risk factors within a tested sample population of the general sports horse population.

OBJECTIVES

To quantify the frequency of saddle slip and to describe the association with lameness, thoracolumbar shape/symmetry, crooked riders and ill-fitting saddles.

STUDY DESIGN

Nonrandom, cross-sectional survey using convenience sampling.

METHODS

Five hundred and six sports horses in normal work were assessed prospectively. Thoracolumbar shape/symmetry were measured at predetermined sites; the presence of lameness (in hand and/or ridden) and saddle slip was recorded. Descriptive statistics, univariable and multiple logistic regression were performed to assess the relationship between horse-saddle-rider factors and saddle slip.

RESULTS

The frequency of lameness, quadrilaterally reduced cranial phase of the stride or stiff, stilted canter was 45.7%, saddle slip 12.3%, left-right thoracolumbar shape asymmetries ≥ coefficient of variance of 8% (1.2 cm) 0.6%; and 103 of 276 riders (37.3%) sat crookedly. The saddle consistently slipped to one side in 24.4% of horses with hindlimb lameness alone, 45.5% of horses with concurrent hindlimb and forelimb lameness, compared with 5.4% with forelimb lameness, 17.4% with stiff, stilted canter, 20% with quadrilaterally reduced cranial phase of stride and 5.5% nonlame horses. Nineteen horses (30.6%) with saddle slip had no detectable hindlimb lameness; however, 14 had a gait abnormality, particularly in canter. Multivariable analysis revealed that saddle slip was significantly associated with hindlimb lameness and gait abnormalities (odds ratio [OR] = 52.62, 95% confidence interval [CI] 17.3-159.7), a saddle fitted with even contact and uniform flocking (OR = 15.49, 95% CI 1.9-125.5), riders sitting crookedly (OR = 6.32, 95% CI 2.9-13.7), a well-balanced saddle (OR = 3.05, 95% 1.4-6.9) and large back shape ratio at T18 (OR = 1.2, 95% 1.1-1.3).

CONCLUSIONS

Many horses with hindlimb and/or forelimb lameness go unrecognised. Saddle slip may be a sign of hindlimb lameness. Education of the equestrian population to identify lameness and saddle slip is required. The Summary is available in Chinese - see Supporting information.

The effect of trotting speed on the evaluation of subtle lameness in horses

Equine lameness is a significant and challenging part of a veterinarian's workload, with subtle lameness inherently difficult to assess. This study investigated the influence of trotting speed on perceived and measured changes in movement asymmetry. Ten sound to mildly lame horses were trotted at a 'slow', 'preferred' and 'fast' speed on a hard surface, both on a straight line and in a circle on left and right reins. Video recordings of the horses were visually assessed by six experienced equine clinicians. Vertical movement of head, withers and pelvis was derived from inertial sensor data and several features calculated. On the straight line, more horses were subjectively declared sound at higher speeds, whilst different objective asymmetry measures showed only slight and inconsistent changes. On the circle, speed had no significant effect on the subjective assessment, with an increase in objectively measured asymmetry at higher speeds possibly balanced by a decrease in sensitivity of the observers for this asymmetry. Horses visually examined for subtle lameness on the straight should therefore be evaluated at a slow speed. Trotting speed should be consistent on repeated occasions, especially during objective gait analysis on the circle, to avoid the interaction of treatment effects and speed effects.

Kinematics of saddle and rider in high-level dressage horses performing collected walk on a treadmill

REASONS FOR PERFORMING THE STUDY

The kinematics of the saddle and rider have not been thoroughly described at the walk.

OBJECTIVE

To describe saddle and rider movements during collected walk in a group of high-level dressage horses and riders.

METHODS

Seven high-level dressage horses and riders were subjected to kinematic measurements while performing collected walk on a treadmill. Movements of the saddle and rider's pelvis, upper body and head were analysed in a rigid body model. Projection angles were determined for the rider's arms and legs, and the neck and trunk of the horse. Distances between selected markers were used to describe rider position in relation to the horse and saddle.

RESULTS

During the first half of each hindlimb stance the saddle rotated cranially around the transverse axis, i.e. the front part was lowered in relation to the hind part and the rider's pelvis rotated caudally, i.e. in the opposite direction. The rider's seat moved forwards while the rider's neck and feet moved backwards. During the second half of hindlimb stance these movements were reversed.

CONCLUSION

The saddles and riders of high-level dressage horses follow a common movement pattern at collected walk. The movements of the saddle and rider are clearly related to the movements of the horse, both within and outside the sagittal plane.

POTENTIAL RELEVANCE

The literature suggests that the rider's influence on the movement pattern of the horse is the strongest at walk. For assessment of the horse-rider interaction in dressage horses presented for unsatisfactory performance, evaluations at walk may therefore be the most rewarding. Basic knowledge about rider and saddle movements in well-performing horses is likely to be supportive to this task.

The effect of rising and sitting trot on back movements and head-neck position of the horse

REASON FOR PERFORMING STUDY

During trot, the rider can either rise from the saddle during every stride or remain seated. Rising trot is used frequently because it is widely assumed that it decreases the loading of the equine back. This has, however, not been demonstrated in an objective study.

OBJECTIVE

To determine the effects of rising and sitting trot on the movements of the horse.

HYPOTHESIS

Sitting trot has more extending effect on the horse's back than rising trot and also results in a higher head and neck position.

METHODS

Twelve horses and one rider were used. Kinematic data were captured at trot during over ground locomotion under 3 conditions: unloaded, rising trot and sitting trot. Back movements were calculated using a previously described method with a correction for trunk position. Head-neck position was xpressed as extension and flexion of C1, C3 and C6, and vertical displacement of C1 and the bit.

RESULTS

Sitting trot had an overall extending effect on the back of horses when compared to the unloaded situation. In rising trot: the maximal flexion of the back was similar to the unloaded situation, while the maximal extension was similar to sitting trot; lateral bending of the back was larger than during the unloaded situation and sitting trot; and the horses held their heads lower than in the other conditions. The angle of C6 was more flexed in rising than in sitting trot.

CONCLUSIONS AND CLINICAL RELEVANCE

The back movement during rising trot showed characteristics of both sitting trot and the unloaded condition. As the same maximal extension of the back is reached during rising and sitting trot, there is no reason to believe that rising trot was less challenging for the back.

Motion pattern analysis of gait in horseback riding by means of Principal Component Analysis

As a consequence of the three interacting systems of horse, saddle, and rider, horseback riding is a very complex movement that is difficult to characterize by a limited number of biomechanical parameters or characteristic curves. Principal Component Analysis (PCA) is a technique for reducing multidimensional datasets to a minimal (i.e., optimally economic) set of dimensions. To apply PCA to horseback riding data, a "pattern vector" composed of the horizontal velocities of a set of body markers was determined. PCA was used to identify the major dynamic constituents of the three natural gaits of the horse: walk, trot, and canter. It was found that the trot is characterized by only one major component accounting for about 90% of the data's variance. Based on a study involving 13 horses with the same rider, additional phase plane analyses of the order parameter dynamics revealed a potential influence of the saddle type on movement coordination for the majority of horses.