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.

Back problems are important contributors to poor performance in sport horses. It has been shown that kinematic analysis can differentiate horses with back problems from asymptomatic horses. The underlying mechanism can, however, only be identified in a uniform, experimental setting. Our aim was to determine if induction of back pain in a well-defined site would result in a consistent change in back movement. Back kinematics were recorded at a walk and trot on a treadmill. Unilateral back pain was then induced by injecting lactic acid into the left longissimus dorsi muscle. Additional measurements were done subsequent to the injections. Data were captured during steady state locomotion at 240 Hz using an infrared-based gait analysis system. After the injections, the caudal thoracic back was more extended at both gaits. The back was also bent more to the left at both gaits. However, at the walk, there was a reversed pattern after a week with bending of the back to the unaffected side. Horses with identical back injuries appear to show similar changes in their back kinematics, as compared to the asymptomatic condition. Unilateral back pain seems to result in an increased extension of the back, as well as compensatory lateral movements. Back movements are complex and subtle, and changes are difficult to detect with the human eye. Present-day gait analysis systems can identify changes in the back movement, and knowledge of the relationship between such changes and the site of injury will be of help in better localising and diagnosing disorders of the equine back.

2006). The effect of weighted boots on the movement of the back in the asymptomatic riding horse. Equine and Comparative Exercise Physiology, 3, pp 13-18Abstract 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 , 0.05. Weighted boots on the hind limbs increased the ROM for dorsoventral flexion and extension in the lumbar back at the walk and decreased the ROM for lateral bending at the thoracolumbar junction at the trot. Weighted boots on the forelimbs decreased the ROM for lateral bending at the withers at the trot. Knowledge of the effect of weighted boots on the back movement is useful in training and rehabilitation of sport horses. Weighted boots on the hind limbs at the walk may induce strengthening of the flexors of the lumbar back and increase the flexion-extension of the lumbar back under controlled conditions.

Summary Among the functional disorders of the upper respiratory tract, dorsal displacement of the soft palate (DDSP) is still a major diagnostic challenge. In this study, measurements of tracheal pressure were made in exercising horses with clinical signs of DDSP. Tracheal pressure was recorded via a percutaneously inserted tracheal catheter during exercise on a treadmill with an inclination of 6.25°, at speeds up to 9 m/s. Five horses with clinical signs of DDSP were compared to 20 earlier studied normal horses. In horses with signs of DDSP the tracheal pressure curve had a characteristic appearance. There were a number of short‐duration pressure peaks over a prolonged expiratory phase and an elevated peak expiratory pressure. The inspiratory pressure was within normal limits. These findings support the hypothesis that obstruction of the air passage in DDSP occurs mainly during expiration and the short peaks of the expiratory pressure curve may reflect the vibrations of the edge of the soft palate.

Summary Recording of intratracheal pressure during exercise as a method for evaluating upper airway obstruction in the horse has previously been carried out on the treadmill. In the present study the method was applied to normal horses, outdoors under field conditions, to assess its usefulness for analysis of respiratory problems mainly occurring under racing conditions. The horses examined performed a standardized exercise test during which the intratracheal pressure was recorded with a tape recorder receiving amplified signals from a transducer connected to a percutaneously inserted intratracheal catheter. The exercise test was carried out under three different conditions: with (1) sulky or (2) rider outdoors and (3) on treadmill indoors. The latter test was included for comparison between field conditions and treadmill exercise. From the recordings obtained, several respiratory variables were calculated. The pressure graphs essentially resembled those obtained previously in tests performed exclusively on the treadmill. There were, however, some differences between the reactions of the horses to the three tests, which seem to necessitate a control material studied under comparable conditions. The technique is simple and the equipment for the outdoor tests is comparatively inexpensive, qualities which seem to make these tests suitable for studies of upper airway obstructions in clinical routine. Further, the outdoor tests may permit investigations of disorders of the respiratory tract that occur mainly under racing conditions.