Summary There is a high prevalence of lameness among Standardbred trotters, most commonly caused by noninfectious joint diseases, mainly related to training and competition. In this context, impact‐related shock waves transmitted through the skeleton and joints have been proposed to be one important factor in the development of osteoarthritis. The aim of the present study was to investigate the characteristic pattern of the events immediately following first contact, with a focus on the in vivo transmission of impact shock waves in the distal forelimb. Two horses were trotted by hand over a force plate. Recordings of 3‐D kinematics of the distal forelimb were carried out by use of a 240 Hz video system. Tri‐axial accelerometer data were collected from a bone‐mounted accelerometer on the midlateral side of the third metacarpal bone (McIII) and from another accelerometer attached to the lateral side of the hoof. Force plate and accelerometer data were sampled at 4.8 kHz using a 16‐bit A/D‐converter, synchronised with the kinematic data. The results indicate that the time lapse of the horizontal retardation of the hoof is an important factor in the attenuation of the impact. A shorter period of hoof braking showed higher amplitudes in the longitudinal retardation of McIII and a more rapid oscillation. This makes all parameters that affect the horizontal hoof braking potentially important to the orthopaedic health of the horse.

Summary Trot in hand, working trot, collected trot, passage and piaffe of 6 Grand Prix dressage horses were recorded by high speed film (250 frames/s). Angular patterns and hoof trajectories of the left fore‐ and hindlimbs were analysed and presented as mean and standard deviation (s.d.) curves. Speed and stride length decreased and fore‐ and hind stance phase durations increased with collection resulting in no suspension in piaffe. The diagonal advanced placement was positive in all gaits except for piaffe. Most of the changes in forelimb angular patterns were effects of reduction in forelimb pendulation. The horses did not step under themselves more in collected trot, passage and piaffe than in trot in hand. The stifle and hock joints were more flexed at the start of the stance phase in piaffe and passage than in the other gaits. Flexion of the hock joint at the middle of the stance phase was largest in passage and piaffe. In spite of the limited number of horses the present study confirmed earlier observations of conformation and gaits in dressage horses. Hindlimb pendulation, femur and pelvis inclinations and elbow, carpal, stifle and hock joint angles seem to be the most significant angular measurements for dressage performance.

Summary Reasons for performing study: Earlier studies have developed a clinical tool to evaluate objectively the function of the equine back. The ability to differentiate horses with back pain from asymptomatic, fully functioning horses using kinematic measures from this tool has not been evaluated. Objectives: To compare the kinematics of the back at walk and trot in riding horses with back dysfunction to the same parameters in asymptomatic sport horses. Methods: The kinematics of the back in 12 horses with impaired performance and back pain were studied at walk and trot on a treadmill. Data were captured for 10 secs at 240 Hz. Range of movement (ROM) and intravertebral pattern symmetry of movement for flexion and extension (FE), lateral bending (LB) and axial rotation (AR) were derived from angular motion pattern data and the results compared to an earlier established database on asymptomatic riding horses. Results: At walk, horses with back dysfunction had a ROM smaller for dorsoventral FE in the caudal thoracic region (T13 = 7.50°, T17 = 7.71°; P<0.05), greater for LB at T13 (8.13°; P<0.001) and smaller for AR of the pelvis (10.97°; P<0.05) compared to asymptomatic horses (FE‐T13 = 8.28°, FE‐T17 = 8.49°, LB‐T13 = 6.34°, AR‐pelvis = 12.77°). At trot, dysfunctional horses had a smaller (P<0.05) ROM for FE at the thoracic lumbar junction (T17 = 2.46°, L1 = 2.60°) compared to asymptomatic horses (FE‐T17 = 3.07°, FE‐L1 = 3.12°). Conclusions: The objective measurement technique can detect differences between back kinematics in riding horses with signs of back dysfunction and asymptomatic horses. The clinical manifestation of back pain results in diminished flexion/extension movement at or near the thoracic lumbar junction. However, before applying the method more extensively in practice it is necessary to evaluate it further, including measurements of patients whose diagnoses can be confirmed and long‐term follow‐ups of back patients after treatment. Potential relevance: Since the objective measurement technique can detect small movement differences in back kinematics, it should help to clinically describe and, importantly, objectively detect horses with back pain and dysfunction.

Summary 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 horse's back.

Summary The movements of the individual limbs of 30 clinically sound Standardbred trotters were studied using high‐speed cinematography. At a speed of 12 metres per second (m/sec; 1:23.6 min/km) the mean stride length was 545 cm and the mean duration of the stride was 455 milliseconds (msecs). The stance phase in the forelimbs was 110 msecs and 117 msecs in the hindlimbs. This difference was due to a longer restraint period in the hindlimbs and resulted in slightly shorter swing phases for the hindlimbs. The variations in any particular horse for stride length and for the duration of stride, stance, swing and propulsion were very small (variation coefficient: approximately 2 per cent). For the restraint stage, however, the variation coefficient was around 5 per cent. The variations noted between different horses were generally 2 to 3 times greater than those recorded for the same horse. There was a close correlation between stride and swing phase duration, suggesting that the swing phase was the main contributor to the stride‐time variations of different horses trotting at the same speed. The restraint and propulsion stages did not seem to play an important role in this respect for this group of animals. Résumé Les mouvements individuels des membres de 30 trotteurs Standardbred cliniquement sains ont étéétudiés à l'aide du cinématographe à grande vitesse. A la vitesse de 12 mètres seconde (soit 1m23 seconde 6/10 du kilomètre), la battue moyenne était de 545 cm et la durée moyenne de chaque battue était de 455 millisecondes. La phase d'appui des antérieurs durait 110 millisecondes, celle des postérieurs durait 117 millisecondes. Il en résultait une phase en suspension légérement plus brève pour les postérieurs. Les variations pour chaque cheval en particulier, de la longueur et de la durée de la battue des phases à l'appui, en suspension de soutien, de propulsion, furent très faibles (variations d'environ 2%). Pour la phase de retenue, le coéfficient de variation était d'environ 5%. Les variations observées entre les différents chevaux étaient en général deux ou trois fois plus importants que celles constatées chez le même cheval. On remarque une étroite corrélation entre la durée de la battue et celle de la phase suspension; cette corrélation parait indiquer que la phase en suspension est le principal facteur des variations des temps de battue de différents chevaux trottant à la même vitesse. Les temps de retenue et de propulsion n'ont pas semblé jouer un rôle aussi important dans ces groupes d'animaux. Zusammenfassung Die Bewegung der einzelnen Gliedmassen von 30 klinisch gesunden Trabern wurde anhand von Hochgeschwindigkeits‐filmen untersucht. Bei einer Geschwindigkeit von 12 m/sec (1'23.6“/km) betrug die mittlere Schrittlänge 545 cm und die mittlere Schrittdauer 455 m/sec. Die Stützbeinphase betrug für die Vorderbeine 110 m/sec und für die Hinterbeine 117 m/sec. Der Unterschied ist die Folge eines verzögerten Abhebens der Hinterbeine, was eine etwas kürzere Hangbeinphase nach sich zeiht. Die Variationen beim e...