M. Rhodin

The influence of head and neck position on kinematics of the back in riding horses at the walk and trot

REASONS FOR PERFORMING STUDY A common opinion among riders and in the literature is that the positioning of the head and neck influences the back of the horse, but this has not yet been measured objectively. OBJECTIVES To evaluate the effect of head and neck position on the kinematics of the back in riding horses. METHODS Eight Warmblood riding horses in regular work were studied on a treadmill at walk and trot with the head and neck in 3 different predetermined positions achieved by side reins attached to the bit and to an anticast roller. The 3-dimensional movement of the thoracolumbar spine was measured from the position of skin-fixed markers recorded by infrared videocameras. RESULTS Head and neck position influenced the movements of the back, especially at the walk. When the head was fixed in a high position at the walk, the flexion-extension movement and lateral bending of the lumbar back, as well as the axial rotation, were significantly reduced when compared to movements with the head free or in a low position. At walk, head and neck position also significantly influenced stride length, which was shortest with the head in a high position. At trot, the stride length was independent of head position. CONCLUSIONS Restricting and restraining the position and movement of the head and neck alters the movement of the back and stride characteristics. With the head and neck in a high position stride length and flexion and extension of the caudal back were significantly reduced. POTENTIAL RELEVANCE Use of side reins in training and rehabilitation programmes should be used with an understanding of the possible effects on the horses back.

The effect of different head and neck positions on the caudal back and hindlimb kinematics in the elite dressage horse at trot

REASONS FOR PERFORMING STUDY Dressage involves training of the horse with the head and neck placed in a position defined by the rider. The best position for dressage training is currently under debate among riders and trainers, but there are few scientific data available to confirm or disprove the different views. OBJECTIVE To evaluate the kinematic effects of different head and neck positions (HNPs) in elite dressage horses ridden at trot. METHODS Seven high-level dressage horses were subjected to kinetic and kinematic measurements when ridden on a treadmill with the head and neck in 5 different positions. RESULTS Compared to free trot on loose reins the HNP desired for collected trot at dressage competitions increased T6 vertical excursion, increased sacral flexion and decreased limb retraction after lift-off. Further increasing head or head and neck flexion caused few additional changes while an extremely elevated neck position increased hindlimb flexion and lumbar back extension during stance, increased hindlimb flexion during swing and further increased trunk vertical excursion. CONCLUSIONS The movements of the horse are significantly different when ridden on loose reins compared to the position used in collected trot. The exact degree of neck flexion is, however, not consistently correlated to the movements of the horses limbs and trunk at collected trot. An extremely elevated neck position can produce some effects commonly associated with increased degree of collection, but the increased back extension observed with this position may place the horse at risk of injury if ridden in this position for a prolonged period. POTENTIAL RELEVANCE Head and neck positions influence significantly the kinematics of the ridden horse. It is important for riders and trainers to be aware of these effects in dressage training.

Basic kinematics of the saddle and rider in high-level dressage horses trotting on a treadmill

REASONS FOR PERFORMING STUDY A comprehensive kinematic description of rider and saddle movements is not yet present in the scientific literature. OBJECTIVE To describe saddle and rider movements in a group of high-level dressage horses and riders. METHOD Seven high-level dressage horses and riders were subjected to kinematic measurements while performing collected trot on a treadmill. For analysis a rigid body model for the saddle and core rider segments, projection angles of the riders extremities and the neck and trunk of the horse, and distances between markers selected to indicate rider position were used. RESULTS For a majority of the variables measured it was possible to describe a common pattern for the group. Rotations around the transverse axis (pitch) were generally biphasic for each diagonal. During the first half of stance the saddle rotated anti-clockwise and the riders pelvis clockwise viewed from the right and the riders lumbar back extended. During the later part of stance and the suspension phase reverse pitch rotations were observed. Rotations of the saddle and core rider segments around the longitudinal (roll) and vertical axes (yaw) changed direction only around time of contact of each diagonal. CONCLUSION The saddles and riders of high-level dressage horses follow a common movement pattern at collected trot. The movements of the saddle and rider are clearly related to the movements of the horse and saddle movements also seem to be influenced by the rider. POTENTIAL RELEVANCE Knowledge about rider and saddle movements can further our understanding of, and hence possibilities to prevent, orthopaedic injuries related to the exposure of the horse to a rider and saddle.

Effect of lungeing on head and pelvic movement asymmetry in horses with induced lameness

Lungeing is an important part of lameness examinations, since the circular path enforced during lungeing is thought to accentuate low grade lameness. However, during lungeing the movement of sound horses becomes naturally asymmetric, which may mimic lameness. Also, compensatory movements in the opposite half of the body may mimic lameness. The aim of this study was to objectively study the presence of circle-dependent and compensatory movement asymmetries in horses with induced lameness. Ten horses were trotted in a straight line and lunged in both directions on a hard surface. Lameness was induced (reversible hoof pressure) in each limb, one at a time, in random order. Vertical head and pelvic movements were measured with body-mounted, uni-axial accelerometers. Differences between maximum and minimum height observed during/after left and right stance phases for the head (HDmax, HDmin) and pelvis (PDmax, PDmin) were measured. Mixed models were constructed to study the effect of lungeing direction and induction, and to quantify secondary compensatory asymmetry mechanisms in the forelimbs and hind limbs. Head and pelvic movement symmetries were affected by lungeing. Minimum pelvic height difference (PDmin) changed markedly, increasing significantly during lungeing, giving the impression of inner hind limb lameness. Primary hind limb lameness induced compensatory head movement, which mimicked an ipsilateral forelimb lameness of almost equal magnitude to the primary hind limb lameness. This could contribute to difficulty in correctly detecting hind limb lameness. Induced forelimb lameness caused both a compensatory contralateral (change in PDmax) and an ipsilateral (change in PDmin) hind limb asymmetry, potentially mimicking hind limb lameness, but of smaller magnitude. Both circle-dependent and compensatory movement mechanisms must be taken into account when evaluating lameness.

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 riders pelvis, upper body and head were analysed in a rigid body model. Projection angles were determined for the riders 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 riders pelvis rotated caudally, i.e. in the opposite direction. The riders seat moved forwards while the riders 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 riders 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.

Back kinematics of healthy trotting horses during treadmill versus over ground locomotion.

REASONS FOR PERFORMING STUDY Treadmill locomotion is frequently used for training of sport horses, for diagnostic purposes and for research. Identification of the possible biomechanical differences and similarities between the back movement during treadmill (T) and over ground (O) locomotion is essential for the correct interpretation of research results. OBJECTIVES To compare the kinematics of the thoracolumbar vertebral column in treadmill and over ground locomotion in healthy horses. METHODS Six sound Dutch Warmblood horses trotted on a T and O during 10 s at their own preferred velocity (mean +/- s.d. 3.6 +/- 0.3 m/s T and 3.6 +/- 0.1 m/s O), which was the same in both conditions. Kinematics of the vertebral column was captured by infrared cameras using reflective skin markers attached over the spinous processes of selected vertebrae and other locations. Flexion-extension and lateral bending range of motion (ROM), angular motion pattern (AMP) and intravertebral pattern symmetry (IVPS) of 5 vertebral angles (T6-T10-T13, T10-T13-T17, T13-T17-L1, T17-L1-L3 and L1-L3-15) were calculated. Neck angle, linear and temporal stride parameters and protraction-retraction angles of the limbs were also calculated. RESULTS The vertical ROM (flexion-extension) was similar in both conditions, but the horizontal ROM (lateral bending) of the lumbar angles T17-L1-L3 and L1-L3-L5 was less during T locomotion (mean +/- s.d. difference of 1.8 +/- 0.6 and 1.7 +/- 0.9 degrees, respectively, P > 0.05). During O locomotion, the symmetry pattern of the lumbar vertebral angles was diminished from 0.9 to 0.7 (1 = 100% symmetry) indicating increased irregularity of the movement (P > 0.05). No differences were found in the basic linear and temporal stride parameters and neck angle. POTENTIAL RELEVANCE Vertebral kinematics during treadmill locomotion is not identical to over ground locomotion, but the differences are minor. During treadmill locomotion lumbar motion is less, and caution should be therefore taken when interpreting lumbar kinematics.

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

Summary 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.

Rater agreement of visual lameness assessment in horses during lungeing

Summary Reasons for performing study Lungeing is an important part of lameness examinations as the circular path may accentuate low‐grade lameness. Movement asymmetries related to the circular path, to compensatory movements and to pain make the lameness evaluation complex. Scientific studies have shown high inter‐rater variation when assessing lameness during straight line movement. Objectives The aim was to estimate inter‐ and intra‐rater agreement of equine veterinarians evaluating lameness from videos of sound and lame horses during lungeing and to investigate the influence of veterinarians’ experience and the objective degree of movement asymmetry on rater agreement. Study design Cross‐sectional observational study. Methods Video recordings and quantitative gait analysis with inertial sensors were performed in 23 riding horses of various breeds. The horses were examined at trot on a straight line and during lungeing on soft or hard surfaces in both directions. One video sequence was recorded per condition and the horses were classified as forelimb lame, hindlimb lame or sound from objective straight line symmetry measurements. Equine veterinarians (n = 86), including 43 with >5 years of orthopaedic experience, participated in a web‐based survey and were asked to identify the lamest limb on 60 videos, including 10 repeats. The agreements between (inter‐rater) and within (intra‐rater) veterinarians were analysed with κ statistics (Fleiss, Cohen). Results Inter‐rater agreement κ was 0.31 (0.38/0.25 for experienced/less experienced) and higher for forelimb (0.33) than for hindlimb lameness (0.11) or soundness (0.08) evaluation. Median intra‐rater agreement κ was 0.57. Conclusions Inter‐rater agreement was poor for less experienced raters, and for all raters when evaluating hindlimb lameness. Since identification of the lame limb/limbs is a prerequisite for successful diagnosis, treatment and recovery, the high inter‐rater variation when evaluating lameness on the lunge is likely to influence the accuracy and repeatability of lameness examinations and, indirectly, the efficacy of treatment.

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.

The effect of weighted boots on the movement of the back in the asymptomatic riding horse

Back dysfunction is an important reason for impaired performance in sport horses. Limb movements influence the movements of the back and factors affecting the limbs may therefore affect the movement of the back. The aim of the study was to investigate the influence of weighted boots on the fore- and hind limbs on the movement of the back. The back kinematics of eight horses was studied at the walk and trot on a treadmill. The ranges of movement (ROM) of the back were compared intra-individually, using Wilcoxon matched pairs test, when the horses moved with and without weighted boots on the fore- and hind limbs, respectively. Differences were considered significant at P