C. Peham

Coordination Dynamics of the Horse~Rider System

The authors studied the interaction between rider and horse by measuring their ensemble motions in a trot sequence, comparing 1 expert and 1 novice rider. Whereas the novices movements displayed transient departures from phase synchrony, the experts motions were continuously phase-matched with those of the horse. The tight ensemble synchrony between the expert and the horse was accompanied by an increase in the temporal regularity of the oscillations of the trunk of the horse. Observed differences between expert and novice riders indicated that phase synchronization is by no means perfect but requires extended practice. Points of contact between horse and rider may haptically convey effective communication between them.

Electromyographic activity of the longissimus dorsi muscles in horses when walking on a treadmill

The pattern of electromyographic activity of the equine long back muscle at the walk has not yet been reported. The aim of this study was to use surface electromyography to measure activity of the longissimus dorsi muscles of horses walking on a treadmill. Fifteen horses without back pain were used and electromyographs were recorded bilaterally from the longissimus dorsi muscles at the level of T12, T16 and L3. Mean electromyograph activity and mean motion were calculated for each horse. At the walk, only one maximum activity for each longissimus dorsi muscle was detected during each motion cycle and this was highest at T12 and lowest at L3. Activity of the longissimus dorsi muscles at the walk is mainly responsible for stabilisation of the vertebral column against dynamic forces. At T12 the high maximum activity could contribute to the development of muscle pain at this site.

Evaluation of pressure distribution under an English saddle at walk, trot and canter

REASONS FOR PERFORMING STUDY Basic information about the influence of a rider on the equine back is currently lacking. HYPOTHESIS That pressure distribution under a saddle is different between the walk, trot and canter. METHODS Twelve horses without clinical signs of back pain were ridden. At least 6 motion cycles at walk, trot and canter were measured kinematically. Using a saddle pad, the pressure distribution was recorded. The maximum overall force (MOF) and centre of pressure (COP) were calculated. The range of back movement was determined from a marker placed on the withers. RESULTS MOF and COP showed a consistent time pattern in each gait. MOF was 12.1 +/- 1.2 and 243 +/- 4.6 N/kg at walk and trot, respectively, in the ridden horse. In the unridden horse MOF was 172.7 +/- 11.8 N (walk) and 302.4 +/- 33.9 N (trot). At ridden canter, MOF was 27.2 +/- 4.4 N/kg. The range of motion of the back of the ridden horse was significantly lower compared to the unridden, saddled horse. CONCLUSIONS AND POTENTIAL RELEVANCE Analyses may help quantitative and objective evaluation of the interaction between rider and horse as mediated through the saddle. The information presented is therefore of importance to riders, saddlers and equine clinicians. With the technique used in this study, style, skill and training level of different riders can be quantified, which would give the opportunity to detect potentially harmful influences and create opportunities for improvement.

A comparison of forces acting on the horse’s back and the stability of the rider’s seat in different positions at the trot

The aim of the study was to compare the stability of the rider as well as the forces acting on a horses back with different seating positions at the trot (sitting trot, rising trot and two-point seat). The same experienced rider was mounted on 10 sound horses trotting on a treadmill. The kinetic data were recorded with an electronic pressure mat, placed under a well-fitting dressage saddle with no saddle pad. The rider used three different seating positions, each for 20 s. Right forelimb motion was used to synchronise the pressure data with the stride cycles. To determine the riders stability, the movement of the centre of pressure (COP) along the transverse (X) and longitudinal (Y) axes was calculated. The force was taken as the sum of all segments of the pressure pad multiplied by the area of the pressure pad. The maximum force and the X- and Y-deviations were evaluated using ANOVA for repeated measures with a Bonferroni Post hoc test. The stability of the rider in the Y-direction was significantly highest in the two-point seat, followed by the rising trot and the sitting trot, respectively. In the X-direction, there was no significant difference between the three positions. The significantly highest load on the horses back was at the sitting trot (2112 N), followed by the rising trot (2056 N) and the two-point seat (1688 N). The rider was most stable in the two-point seat while transferring the lowest load on the horses back. The rising trot was found to be more stable and less stressful for the horses back compared to the sitting trot.

Limb locomotion — speed distribution analysis as a new method for stance phase detection

The stance phase is used for the determination of many parameters in motion analysis. In this technical note the authors present a new kinematical method for determination of stance phase. From the high-speed video data, the speed distribution of the horizontal motion of the distal limb is calculated. The speed with the maximum occurrence within the motion cycle defines the stance phase, and this speed is used as threshold for beginning and end of the stance phase. In seven horses the results obtained with the presented method were compared to synchronous stance phase determination using a force plate integrated in a hard track. The mean difference between the results was 10.8 ms, equalling 1.44% of mean stance phase duration. As a test, the presented method was applied to a horse trotting on the treadmill, and to a human walking on concrete. This article describes an easy and safe method for stance phase determination in continuous kinematic data and proves the reliability of the method by comparing it to kinetic stance phase detection. This method may be applied in several species and all gaits, on the treadmill and on firm ground.

Kinematic motion analysis of the joints of the forelimbs and hind limbs of dogs during walking exercise regimens

OBJECTIVE To assess forelimbs and hind limb joint kinematics in dogs during walking on an inclined slope (uphill), on a declined slope (downhill), or over low obstacles (cavaletti) on a horizontal surface and compare findings with data acquired during unimpeded walking on a horizontal surface. ANIMALS 8 nonlame dogs (mean +/- SD age, 3.4 +/- 2.0 years; weight, 23.6 +/- 4.6 kg). PROCEDURES By use of 10 high-speed cameras and 10 reflecting markers located on the left forelimbs and hind limbs, joint kinematics were recorded for each dog during uphill walking, downhill walking, and walking over low obstacles or unimpeded on a horizontal surface. Each exercise was recorded 6 times (10 s/cycle); joint angulations, angle velocities and accelerations, and range of motion for shoulder, elbow, carpal, hip, stifle, and tarsal joints were calculated for comparison. RESULTS Compared with unimpeded walking, obstacle exercise significantly increased flexion of the elbow, carpal, stifle, and tarsal joints and extension in the carpal and stifle joints. Only uphill walking caused increased hip joint flexion and decreased stifle joint flexion; downhill walking caused less flexion of the hip joint. During obstacle exercise, forward angle velocities in the elbow and stifle joints and retrograde velocity in the tarsal joint changed significantly, compared with unimpeded walking. Joint angle acceleration of the elbow joint changed significantly during all 3 evaluated exercises. CONCLUSIONS AND CLINICAL RELEVANCE These evidence-based data indicated that each evaluated exercise, except for downhill walking, has a specific therapeutic value in physical therapy for dogs.

Influence of rider on lameness in trotting horses

REASONS FOR PERFORMING STUDY Equine lameness is commonly evaluated when the horse is being ridden, but the influence of the rider on the lameness has not been documented. OBJECTIVE To document the effect of 2 riders of different training levels on the vertical movement of the head and croup. METHODS Twenty mature horses were ridden at trot by an experienced dressage rider and a novice rider, as well as trotted in hand. Kinematic measurements of markers placed on the horses head and sacral bone were carried out. The asymmetries of the vertical head and sacral bone motion were calculated as lameness parameters and compared with paired t tests. RESULTS Trotting in hand, 17 horses showed forelimb lameness (1-4/10) and 13 hindlimb lameness (1-2/10). Intra-individually, 11 horses showed significant differences in forelimb lameness and 4 horses showed significant differences in hindlimb lameness when ridden. Over all horses, hindlimb lameness increased significantly under the dressage rider compared to unridden horses. CONCLUSIONS The presence of a rider can alter the degree of lameness; however, its influence cannot be predicted for an individual horse. POTENTIAL RELEVANCE In order to evaluate mild lameness, horses should be evaluated at trot both under saddle and in hand. If lameness is exacerbated, a second rider may be helpful; the level of training of the rider should be taken into consideration.

Fourier analysis of vertical ground reaction forces in dogs with unilateral hind limb lameness caused by degenerative disease of the hip joint and in dogs without lameness.

OBJECTIVE To evaluate the applicability of Fourier analysis for assessment of ground reaction forces (GRFs) and differentiation between dogs with unilateral hind limb lameness caused by degenerative joint disease of the hip (DJD-H) and dogs without lameness. ANIMALS 37 dogs with or without unilateral DJD-H. PROCEDURES Data were obtained from other studies and analyzed retrospectively. Among the 37 dogs, 20 had unilateral DJD-H and 9 (non-Belgian Malinois breeds) had no lameness; another 8 were nonlame Belgian Malinois (radiographically confirmed Fédération Cinologique International classification A [ie, no hip dysplasia or DJD-H]). Gait data acquisition was performed as dogs walked on a treadmill with integrated force platforms. The peak vertical force, mean vertical force, and vertical impulse were compared among the 3 groups. Fourier analysis was performed on the force-time curves for the vertical GRF, and calculated Fourier coefficients were compared within and between groups. RESULTS Lameness in the hind limbs with DJD-H was detectable via conventional analysis of the GRF as well as via Fourier analysis. However, subtle gait aberrations in the forelimbs of the dogs with DJD-H were detected solely via Fourier analysis of GRFs and remained undetected via conventional analysis. CONCLUSIONS AND CLINICAL RELEVANCE Results support the applicability of Fourier analysis for evaluation of force-time curves of GRFs. Fourier analysis can reveal subtle alterations of gait that might otherwise remain inapparent; however, further investigation is necessary before this method can be routinely applied for lameness detection in dogs.

An assessment of the pressure distribution exerted by a rider on the back of a horse during hippotherapy.

Hippotherapy employs locomotion impulses that are emitted from the back of a horse while the horse is walking. These impulses stimulate the riders postural reflex mechanisms, resulting in training of balance and coordination. The aim of the present study was to assess the changes in magnitude and distribution of the contact pressure between the rider and the horse during a series of hippotherapy lessons. The monitored group, consisting of four healthy women (mean age 22.75 years, mean body weight 59.75 kg, mean height 167.25 cm) without any previous horse riding experience, received five 20 minute-lessons lessons in a three-week period. Hippotherapy was given on a 15-year-old thoroughbred mare. An elastic pad (Novel Pliance System, 30 Hz, 224 sensors) was used for pressure magnitude evaluation. The maximum pressure value was increased (p<.05) in the event of a second measurement (5th lesson). The pressure exerted on the rider upon contact of the rear limbs was higher than upon contact of the front limbs (p<.01). The size of the center of pressure (COP) deviations in the anteroposterior direction reduced (p<.05) with the number of lessons received. With the growing experience of the participant, an increase in pressure occurred on contact of her body and the horses back as well as in the stability of the COP movement.

Compensatory load redistribution in naturally occurring osteoarthritis of the elbow joint and induced weight-bearing lameness of the forelimbs compared with clinically sound dogs.

The current study investigated the compensatory load redistribution due to osteoarthritis of the elbow joint using ground reaction forces of all four legs, simultaneously measured on a treadmill with integrated force plates. Three groups of dogs were used: the first group was clinically sound; the second group suffered from a naturally occurring osteoarthritis of the elbow joint, and a reversible lameness was induced in the third group. The naturally occurring osteoarthritis resulted in a compensatory gait pattern to reduce the stress on the affected limb. The load was reduced on the lame limb and increased on the contralateral hindlimb. The symmetry index indicated a weight-shift to the contralateral forelimb and diagonal hindlimb, which resulted in a more balanced weight distribution than in normal dogs. Dogs with induced lameness showed comparable but less pronounced alterations. These results suggested that forelimb lameness could lead to overload on non-affected extremities and the vertebral spine.